: Differential Dilemma



Timothy60
03-21-07, 09:56 AM
I have a question about my 1993 Fleetwood with 168,000 miles on the clock. I removed the plug on the differential housing and checked the oil inside and it is OK. In your opinion, is it a good idea to drain all the oil from the differential and replace it with fresh oil? --OR-- is it best to just leave well enough alone? (It is not making any noises or doing anything unusual.) What would you do?Thank you for your comments and advice.

BCs71
03-21-07, 12:23 PM
If it was my car, I would change the fluid by removing the cover and making sure to remove all metal particles inside. Replace with new gasket and 2 1/2 quarts of gear oil and you're all good, even if it is just for peace of mind.
SHould cost about $10 and an hour of your time.,

jayoldschool
03-21-07, 02:07 PM
Don't forget the limited slip additive from GM if you have option G80. Two bottles.

caddycruiser
03-21-07, 07:13 PM
Don't forget the limited slip additive from GM if you have option G80. Two bottles.

No '93-96 Fleetwood ever had this from the factory, so not at all a concern.

But, as BCs71 said, it's best to take the cover off, completely re-do the fluid and use a new seal, the latter especially since most had a badly designed seal from the factory that can lead to some issues. If it's never been changed and over 100k, probably all a good idea.

N0DIH
03-21-07, 08:04 PM
I thought G80 was available in 1993, but not 1994-1996.

Yes, by all means, change fluid in the diff every 50K or so, more if you tow....

ShadowLvr400
03-21-07, 08:32 PM
I thought the V4p was a posi...

jayoldschool
03-21-07, 09:48 PM
Oops, forgot that. Too much time in my G80 equipped 95 SS.

V4P is the trailer package.

N0DIH
03-22-07, 01:57 AM
I had thought V4P in 93 got the G80 std, but I wasn't sure. But in 94-96 V4P, it isn't allowed, along with the rest of the D Body carline.

Timothy60
03-22-07, 09:39 AM
Thanks for the advice. OK, I'm convinced. I'll change the differential lubricant the next time I change the oil. Maybe Amsoil has a lubricant designed for differentials so I'll look into that since that's what I have in the tranny with good results.

N0DIH
03-22-07, 10:06 AM
I have run Amsoil 750W90 for years. In my 80 T/A with a 455 the car was noticeable faster from 60 mph+ after the swap compared to the dino 80W90 that was in there previously.

Rob Benham
03-24-07, 08:20 PM
Does this oil fall into the 'Hypoid' (spelling?) catagory?

Years ago on my Turbo Supra the oil smelled like old lorry oil from WWII but the diff was a weak link in what whas otherwise a super car.

scurling
03-24-07, 08:53 PM
My 2 centavos: The fill plugs are magnetic. If you removed the plug and it didn't have a lot of fine metal, you shouldn't have a problem. I can count on one hand the number of passenger car rear ends I've seen fail since '55. The average person never changes the oil unless there is a leak that need repairing. I think taking the cover off invites more potential problems than it will prevent.

Most of the 4 wheel drive SUV mauals I've seen even state to never open the fill plug unless you see a leak. The oil isn't going anywhere.

The Ape Man
03-24-07, 09:08 PM
Leave it alone is right on. Gear lube doesn't get contaminated like engine oil from unburned gasoline or trans fluid from the trans innards wearing. The only exception would be if the car was under water.

Timothy60
03-26-07, 09:46 AM
When I took out the filler plug, there were no metal particles on it; it was very clean. I did not realize that it was magnetic! So I suppose this differential issue is like many others. Some people say change the lubricant, others say leave well enough alone. So. . . it's OK to change it, but it's not doing any harm if I don't. I suppose that in any case, it's not an emergency. Maybe I should be thankful it's the only issue I have to think about with a car that has 169,000 miles on it and still looking/running great. Thanks for your input.

scurling
03-26-07, 01:00 PM
Tim

Don't get me wrong, I know we like to work and tinker on our vehicles. I'm no different, I just don't have the time ..(or energy) that I use to.

IMHO, from a purely maintenance point of view, I don't think changing the oil is necessary and many maintenance schedules don't want the owner to open the fill plug unless a leak is visibly present. Will it hurt anything? Of course not, but if you change it, just be very clean about your work. Clean the outside of the housing thoroughly before opening it up. You know how much dirt, rust flakes, etc. gets kicked around when working under the car. You don't want any foreign particles to fall into the diff. housing.

soxx35
03-26-07, 06:08 PM
the fill plug is not magnetic but there is a magnet in the differential. Also if it has the original differential cover gasket in its the wrong one from the factory. The new ones have extra holes to lube the axles. But since you have 163k on it already you probly dont have a problem. But still good to change to the updaded regardless.

Timothy60
03-27-07, 12:36 PM
Good point about dirt contamination from underneath the car, Scurling. After reading your post, I thought that I'd just leave the differential alone. But take a look at the post by Soxx35. What's up with the gasket being wrong from the factory? I never heard anything about that. How can extra holes in a gasket help lubricate the axle shafts? Do all 93's need to have an updated differential gasket installed?

N0DIH
03-27-07, 01:16 PM
Yes, my 94 had the wrong gasket, and that is why I have a pair of toasted axles to prove the damage it can do. I have a 0.15 or inch groove in my axles now, my left side I can't stop the oil leak anymore. Mine went 160-180K on the wrong gasket. This axle should last much longer if it had the right gasket. I have heard that some axles got wiped in 50K miles over it.

GM screwed up and let buyers source the gasket and not engineering, so no one looked at the drawings to verify it was compatible. Just like the broken exhaust manifold bolts. Stupidity letting bean counters source parts without engineering approvals...

Brother_B
03-27-07, 11:58 PM
Stupidity letting bean counters source parts without engineering approvals...

If I had a nickel...:highfive:

BCs71
03-28-07, 12:55 PM
What's up with the gasket being wrong from the factory? I never heard anything about that. How can extra holes in a gasket help lubricate the axle shafts? Do all 93's need to have an updated differential gasket installed?

Soxx35 is correct. Check this out about the diff gasket.

http://www.theherd.com/articles/felpro.html

N0DIH
03-28-07, 04:08 PM
I got bit by it, just ordered my new axles yesterday.... mine are shot.... So bad I can't even get the left side out it is so deep in the groove.

Mine went 160K miles or so on the bad gasket.

Timothy60
03-29-07, 09:56 AM
Wow! That is amazing information about the gasket. A GASKET!!! Who would ever think something so cheap could cause a major problem! Now I'm wondering about the gasket on my '93. Is there a way to tell if it still has the original gasket? With 169,000 miles, is the axle on its way to failure? Do you mean to say that the axle has not had proper lubrication at any time during its service life so far???

N0DIH
03-29-07, 10:07 AM
Pull it, unless you can document that the gasket was ever changed. Pull it sooner than later, it really matters.

Mine got replaced at 150-180K miles and was wrong, and at 210 I started getting a oil leak at the pass side axle seal. I put in a new axle seal and no dice, she is still a leaker. There is just too much wear and the axle pushes up into the bearing and breaks the seal. New axles are only fix. They are $158 through Dal. Expect to drop around $350 for a pair mail order. $180+ local dealer, list is $238 each. Can we owch???

jayoldschool
03-29-07, 11:24 AM
They might be cheaper through Moser.

I went through this on my old 9C1 Caprice. Had to do one axle when I got it. Luckily, the ones in my Impala SS were ok when I installed the 4.10s after putting in my T56 six speed. I made sure to use a fresh, correct, gasket.:thumbsup:

N0DIH
03-29-07, 12:45 PM
For a 93 and older maybe, but for a 94-96, they won't have. It is unique to the Fleetwood only. It has the ABS/Traction Control relucutor ring that the B Bodies don't have.

BCs71
03-29-07, 01:11 PM
Wow! That is amazing information about the gasket. A GASKET!!! Who would ever think something so cheap could cause a major problem! Now I'm wondering about the gasket on my '93. Is there a way to tell if it still has the original gasket? With 169,000 miles, is the axle on its way to failure? Do you mean to say that the axle has not had proper lubrication at any time during its service life so far???
That article is a bit old now, IIRC, and doesn't state anything about how Felpro isn't the ONLY manufacturer of good (correct) gaskets nowadays.
A couple years ago Napa had their own brand on the shelf with correct lub holes for the axles.

Basically, the gasket you need will have a small hole in both the three and nine o'clock positions to allow diff lube to pass through and into axle shafts.

N0DIH
03-29-07, 01:39 PM
NAPA has 2 gaskets too, I like the more expensive one (like $10), it is a NICE gasket and I have reused with no issues.

Felpro isn't the only one correct, but you must examine it for the small holes. Line up to the axle and you will see how they line with the gasket.

You can mod any "wrong" gasket too, if any still exist.

I think it was only GM gaskets that were wrong.

Timothy60
03-30-07, 09:39 AM
Good job.Thank you for the information. I'm convinced. I'm going to replace the gasket on my '93 ASAP with the hope that the new gasket will prevent the expensive problem Nodih has had with his. The mileage sounds eerily similar; mine has 169,000 miles. Here's one last question: if the original gasket prevents lubricant from reaching the axle bearings, why would they last 169,000 miles with no obvious sign of trouble?

N0DIH
03-30-07, 12:41 PM
I don't mean to sound negative, I was hoping the same thing, that if I hadn't had a problem by 170K I was ok, but by 200-210K, I was having a problem. Immediately after changing the synthetic gear lube even, I got axle noise in heavy corners where I didn't before. Chances are the damage is done, it is a matter of time till the seals can't handle it and leak.

I later found I had a broken pinion lock bolt and my pinion lock shaft was moving around beating things up inside the carrier, so that isn't cool either. I had another shaft and lock bolt to put in and all is fine now.

So hopefully the posi will go in with the new axles very soon.

Next time the car is up for brakes, lift up on the axle shaft. It shouldn't go up... Mine around 0.2in up and down...

Timothy60
03-30-07, 01:04 PM
Nodih, I know the passenger side axle shaft DOES have some play on my car; I noticed it the last time I had the drums off but just figured it was normal wear and tear. The left axle is OK, however. Yes, the damage has most likely been done. I'm still going to put on the new gasket. Maybe it will prevent it from failing the way yours did. Good luck installing your posi.

The Ape Man
03-31-07, 12:16 PM
My BS meter is pegged on this. Axles used as races for bearings are poor design. They wear quickly. This has been a problem for Cadillac since 1977. Maybe the actual trouble was from a different (read cheaper) hardening process used on the axles themselves. This could account for a model year failure rate change. The article cited makes at least one gross oversimplification about how axles always wore out by XX miles in fleet service. That throws up a red flag. Every vehicle in the fleet would have to be rotated by users in order to get uniform failures like that. They are later able to conclude how axles lasted at least 50% longer after enactment of their new service schedule. Sorry but this reads a whole lot like some middle management justify my job junk science. A little corkscrew tin sleeve pressed onto the axle near the spline end could have channeled a whole lot of oil out toward the bearings. Has anyone manufactured an axle for the same service that was used as a bearing race and lasted???

N0DIH
03-31-07, 10:58 PM
My 80 T/A at 70K or so miles (last time I pulled the axles) had no visible wear. And I corner like a madman in that car. That is with 455 power for good time, and the 301 Turbo making est 290 RWHP the rest of the time. It was well abused... I personally have never seen a F Body axle worn like that (then again, I haven't seen THAT many either), but even junkyard axles were always in excellent shape wear wise.

The author is a very sane person and quite knowledgeable. Might be able to get a hold of Katshot, maybe he can enlighten us from the Limo standpoint. I can see if I can find his old lurking grounds....

Personally you could be right, GM could have got just plain crappy and cheap from 77-up and didn't heat treat things well and that contributed to the problems. I would still rather see something like the bolt in axles that Ford and Pontiac/Olds axles used would be the preferred.

The 8.5" axle has lasted for a LONG time in GM's inventory. Even my 96 Suburban at 190K miles had no appreciable wear either, stock axles. I'll lurk around the truck forums on this, the 8.5"/8.6" is quite popular in trucks....

Timothy60
04-02-07, 01:44 PM
Yes, it would be interesting to hear the viewpoint of someone who has expertise in fleet or limo maintenance. My BS meter is pegged on this one, too. What's the truth?

N0DIH
04-02-07, 01:52 PM
Best I can tell from the truck community is no one has heard of the problem. So either the got the right gasket or didn't use a gasket and used gasket goo. But look here and you can see WHY this is an issue.

Those holes are blocked by the gasket. Those are the access to the axle tubes to pump in oil.

Time to get the BS meter tweaked. I have never seen axle problems like this on any GM car with this style axle that ever had the right gasket that didn't block these holes. But the carline that got these holes blocked had issues.

Thanks to WhiffleBat on FullsizeChevy.com for the excellent photo.

Timothy60
04-03-07, 09:39 AM
Thanks for the research, Nodih. I don't think anyone needs more solid evidence. My question is, "Why did GM allow such a glaring mistake to continue?" I take that back. . . I know the answer to that question and it really shakes my confidence in GM products. I'm disgusted. I think if GM had spent $100 more per vehicle in quality assembly and components, the final Fleetwood series could have been a truly noteworthy automobile.

N0DIH
04-03-07, 09:54 AM
Engineering designed the axle way back in the 60's and probably didn't do any updates till the 8.6" gear in 199x. Being the group is likely disbanded and something like this is a minor part, sourcing probably sourced a new lower cost part from some new vendor and no one did a first article inspection (FAI) on the incoming parts and the parts went straight on to the production line.

Being American Axle manufactured the axle for GM, the problem probably wasn't GM directly, and was AA fault.

So, with AA screwing up the gasket, GM not doing a 100% teardown of the incoming axles at some point (why would they?) and then finding the problem at a later date, I am sure there is a slew of GM 5 Phase (similar to Ford 8D) on it, but the general public is just plain screwed on it. Being GM will put the pain to the suppliers for 10 years, the end customer only gets 3 years at best of warranty coverage.

So directly not GM's fault, but being the car was purchased from GM, it is their responsibility. But being they don't give a rats behind on what gets out the door after the warranty, we are the end user who gets screwed. The quality just wasn't there.

It comes down to not being spec'd properly, not inspected properly, and GM trying to sweep it under the rug as much as they could to avoid an all out recall....

Timothy60
04-04-07, 12:44 AM
Pull it, unless you can document that the gasket was ever changed. Pull it sooner than later, it really matters.

Mine got replaced at 150-180K miles and was wrong, and at 210 I started getting a oil leak at the pass side axle seal. I put in a new axle seal and no dice, she is still a leaker. There is just too much wear and the axle pushes up into the bearing and breaks the seal. New axles are only fix. They are $158 through Dal. Expect to drop around $350 for a pair mail order. $180+ local dealer, list is $238 each. Can we owch???
OK, I went to NAPA and bought the correct gasket today after work. It cost $4.99 including tax. It has the two slots for the corresponding oil passages. Great. But this is what I don't understand: If NODIH's car had the WRONG gasket (without the slots), how does the oil leak out of the axle seal if no oil can get past the gasket in the first place?

N0DIH
04-04-07, 02:36 PM
Some oil will get there, but not enough. As the oil gets "pumped" to the axle tubes, some will drain back into the sump under the ring gear, and some will eventually to the axle bearings as you drive. Being the sump is below the axle tubes, there is no way for oil to get into the axle tubes. So the oil kicked up from the ring gear onto the inspection cover and drain down into those holes is the only way. So block those holes and you see the major problem. No oil can GET there.

$5, you got the "cheap" gasket, the paper thin one. The $10 one is the nice thick cork gasket. It seemed like it has some other "features" too, but I don't remember. The $10 gasket was a much nicer one, I would buy it again given the choice. But being more $$, people don't buy, so it isn't in stock often.

JTraik
04-05-07, 09:00 AM
Leave it alone is right on. Gear lube doesn't get contaminated like engine oil from unburned gasoline or trans fluid from the trans innards wearing. The only exception would be if the car was under water.

So it stays clean, but the hydrocarbon chains that make up oil are sheered apart after a certain amount of use. Even Amsoil systems have a limit... it can keep it clean but eventually the oil is completely sheered.

Now another thing is, i've been working at a Rolls Royce repair shop and I get into discussions with the owner frequently on topics like this. One of his RR's has upwards of 450k on it. The rearend has never been rebuilt and this has been accredited to his meticulous car maintenance part of which includes changing the diff oil every 10k (ten thousand)...

N0DIH
04-05-07, 09:34 AM
I thought GM severe service was around 30K mile changes and 60K normal service?

Or was it 15K and 30K? It is one of the most abused/ignored oil changes.

Oils do fail over time, the more the severe service the shorter the life. The oils evaporate, shear/breakdown and the viscosity increases. So as it gets older and older it will get thicker and thicker, reducing gas mileage.

I haven't swapped the oil in my Suburban rear end yet, but plan to soon. It is the monster 10.5" corporate GM rear. My Cad is like most with the 8.5". I have swapped the gear oil 2x in the last 30K. Mainly from the second time having to replace the axle seal so it had to come back out. I did save some of it as it was synthetic, but the rest was good old 80W90 dino oil...

Timothy60
04-05-07, 09:52 AM
Yes, I think it's time to drain and refill the differential at 169,000 miles. I was torn between the "leave it alone" philosophy and changing it, but not any more. (the R-R 10K change interval is a bit radical, however!) Thanks for the information. I can't argue with the idea that the lubricant has undoubtedly degraded at this point, and the gasket issue itself is compelling, too. From everything I've read here and other places, I've decided not to put in a synthetic oil but stick with dino as a replacement. I'm still outraged at GM, however, for assembling this component with an improper gasket that impedes proper bearing lubrication requirements.

JTraik
04-05-07, 12:43 PM
(the R-R 10K change interval is a bit radical, however!)

If you watched this guy work for a day, that would be the least radical thing he could possibly do. He is a restorationist and a Judge of Judges at Rolls-Royce/Bentley shows. Learned a ton from him!

N0DIH
04-05-07, 03:12 PM
Just remember, GM just missed it, It was American Axle's fault, GM just didn't catch it till the warranty failures spiked.

rlyons
04-07-07, 10:21 PM
I would suggest everyone check their gaskets if you have not already changed it as I did mine today and sure enough it did not have the correct gasket and the holes were covered. I can see where that is a problem. I was lucky as mine only has 67,000 miles and my axle bearings are good and tight. I now have the piece of mind knowing that it has fresh oil and the correct gasket.

N0DIH
04-08-07, 05:20 PM
You cannot go wrong by changing it if there is ANY question that it has not been done....

N0DIH
04-08-07, 09:01 PM
Just checked my diff oil. Was down enough that I had to add around 3/4 qt. And that in only a few months. Scary.... No wonder it keeps getting noisy after 40 miles or so of running......

Timothy60
04-12-07, 03:23 PM
OK, I'm going to make a prediction! Because I have the day off tomorrow, I'm going to remove the differential cover on my 93 Fleetwood, drain the old lubricant, and install the correct Fel-Pro gasket (with the slots). I have the Amsoil already to put into the differential. This is my prediction: within a few hundred miles (maybe even sooner!) the lubricant will find its way through the newly-found slots and down the axle tubes. Wow! It's never been there before! Guess what's going to happen next? IT'S GOING TO START LEAKING FROM THE PASSENGER SIDE SEAL. What do YOU think? Comments and bets are welcome. I am very, very, very tempted to cancel this whole project for tomorrow and leave the differential alone.

N0DIH
04-12-07, 03:27 PM
How many miles on it?

Mine got the oil changed @ 170ish and didn't start leaking till 210ish. And one side did, one side didn't. The one side that didn't is the noisy side and the one I can't even get out.

Heck, simple enough while you are in there, pull the axles out and look at them for damage. Drop wheels, pull drums, pull pinion lock, pull pinion lock shaft, push axles IN and remove c-locks, then pull out and examine closely.

Mine were BAD (the one I could get out). The DS is so bad I can't even push it in far enought to pull the c-clip off.

Timothy60
04-12-07, 08:09 PM
My Fleetwood will turn 170,000 this coming week. So maybe I can expect 40,000 more miles until the seals start leaking? OK, we'll see what happens on that one! No, I'm not going to take the axle shafts out because that will take me all day to do, although I am CURIOUS! You make it sound simple, but I'm not sure if I can do it. If I screw something up, I can't get to work. That's the gauge I use to measure the maximum level of complexity I dare venture into.

"If you want to understand something, make it." --Sir Alfred North Whitehead

N0DIH
04-12-07, 08:29 PM
No way to know. GM saw warranty failures for this with under 50K miles. No way to know when or if it will ever leak. Mine makes noise, but honestly, didn't until I changed the oil (went from factory oil to Amsoil 75W90) and corrected the gasket. Any gasket is fine as long as it has the holes. Doesn't have to be FelPro. I used the NAPA "deluxe" one, $10ish. It is a very nice gasket. The $5-$6 is plain cardboard type. Permatex works fine too, done that for many many years and have had no leaks.

Just jack up the back end up and lift the wheels up and down (yeah, I know hard. Much easier with wheels off), if they go up then there is wear. Once it exceeds the seals capability of staying around it, it leaks. Even a new seal on mine can't seal it, it is that bad.

Timothy60
04-17-07, 09:47 AM
OK, I changed the differential oil. Mileage:169,000. I thought that when I removed the cover, the oil would be all cruddy but it wasn't! It was the color of honey and very clean. There is a circular magnet attached to the inside of the differential cover. It was covered with a little bit of fuzzy-looking metal. While the oil was dripping out, I cleaned up the diff cover and removed the remaining bits of gasket. Yes, it was the WRONG gasket installed at the factory! Now I have the correct gasket installed (with the slots) and a differential filled with fresh Amsoil lubricant. Now I just hope it doesn't start leaking! Thanks for all your help.

N0DIH
04-17-07, 09:55 AM
That fuzzy grey goo is something I have always seen. I think it is just a product of the metallic wear seen inside. I always clean it up, clean up the sump (the resovoir below the ring gear).

If you want to flush it, fill with 30wt engine oil, re-install cover, drive in a figure 8 very gently for a few times, very gentle on throttle, and then drain and fill with gear oil. This from my 1976 Olds FSM. Again, GENTLE on the throttle! Don't exceed 30 mph.

Old Fleetwood
04-17-07, 12:08 PM
WHOA!
That flush procedure is something new that I'd never seen before.
THANKS!:thumbsup: :thumbsup:

JTraik
04-17-07, 12:48 PM
If you want to flush it, fill with 30wt engine oil, re-install cover, drive in a figure 8 very gently for a few times, very gentle on throttle, and then drain and fill with gear oil. This from my 1976 Olds FSM....

And never to be heard from again.... seems like a waste of time and also risks damaging your gasket you just bought through process of reinstallation.

Also someone else mentioned that they thought that the outer bearings run dry without the "proper" gasket. I think this to be un-true. The only acting barrier between the differential housing and the axle tubes are the inner bearings/races..... now why this is of any importance is still a bit of a mystery to myself.... There will still certainly be oil getting to the outer bearings... perhaps not just as much. If you examine the actual differential cover you will notice contours shaping up to the slits. When the vehicle is in forward motion the ring gear will rooster-tail oil radially, most of this will be directed towards the pinion bearings, and the remaining mass or pool of oil, i think, would be shifted and risen above the level of the slits essentially pumping oil to the tubes and draining through the inner bearings.


I think this would explain why these rear's run so long even with the wrong gasket... is because they are getting oil, just not enough at higher speeds. I have no idea if thats how it works, it makes sense to me though and thats how I would engineer it. What do you guys think?

N0DIH
04-17-07, 01:02 PM
You obviously have NEVER looked that close. AND you haven't had one fail, like mine. These axles should last well over 300K, even to 400K with NO issues. They do NOT. The trucks have always had the RIGHT gasket and have NO FAILURES. The B/D cars have had massive failures

What part does everyone just not understand?? GM even admits this to the commercial segement, limo/cop cars/taxis. So why is it so darn difficult to understand that this is a REAL PROBLEM?????????????????

7.5" axles, not an issue, OEM used gasket goo
8.5" axles, ISSUE.
9.5" axles, not an issue, they got the right gasket.

I will dig up my picts and show you the damage.

Look at the pictures of the rear axle housing on the first page of this thread. (http://www.cadillacforums.com/forums/rwd-19xx-1985-deville-fleetwood-1985/102320-differential-dilemma.html). Is it that hard to see???

Sorry, I am fed up with people who have never pulled their own axles to look and to think that gear oil is a lifetime lube. It is NOT. GM specs this to be changed around 50K miles. It is one of the most neglected maint items.

Old Fleetwood
04-17-07, 01:20 PM
Ergo, instead of a gasket, what about using gasket glop? :confused: :confused:

N0DIH
04-17-07, 01:23 PM
and if you flush, just use old gasket, I have had great resuse of gaskets as long as they aren't damaged.

Goo is fine too, excellent reliability and easy cleanup in most cases. Get Ultra Grey, it is great stuff, Olds used it OEM on the 307 valve covers too (NO GASKETS!! IF you have valve cover GASKETS on a 307, they have been off)

JTraik
04-17-07, 10:56 PM
Hey man no one is denying the problem. I have a freakin axle assembly on the side of my garage that got trashed because of those damn gaskets. I can take pictures of my destroyed axle shafts and can show a short clip of how my pinion spins freely because the bearings are so worn down, the preload is gone. What my point is, that axle didnt get trashed until it had 100k on it.

Obviously change the oil... I dont know about that flush sequence though, still seems like a waste of time.

Timothy60
04-18-07, 12:38 PM
It's true that SOME oil does go past the inner bearings into the axle tubes. I suspect (although I can't corroborate this statistically) that most failures concerning the 8.5" axle transpire under heavy bearing load conditions such as sustained high-speed operation, trailer towage, or chronic abuse. That may be why fleet/police applications of this typically durable axle assembly have been particularly vulnerable to outer bearing/seal failure: extreme operational loads amplify the problem. I suggest that most 8.5" axle assemblies, even with the incorrect gasket, have delivered an acceptable service life to the operator. Please remember that most 1990-96 B and D body vehicles are now well beyond the expected service life for which they were marketed and sold.

Raider1v1
04-18-07, 02:24 PM
hey guys, sorry to get a little off topic, but i cant seem to find this info anywhere!

i have a 69 deville, with the controlled diff. its not a positrack so i dont need the additives right? i called 4 Cadillac dealers around me and i was looking in the service manual. the only thing i found was there was "special lubricant" for it but all the dealers said just use the 90w gear oil. back then there wasnt the additives.

what do you think? id appreciate any help

N0DIH
04-18-07, 02:38 PM
Remember the names are marketing names. Controlled differential (Cadillac), Posi traction (Chevy), Limited Slip (Buick?), AntiSpin (Olds), Safe-T-Trac (Pontiac), Twin Grip (AMC), etc. There are only a couple TYPES of differentials that fall into the limited slip class, and a few in the locker class.

GM has used Cones and Clutch type differentials. Cones are smoother, but once worn, the diff is shot. Clutches are fully rebuildable but are more prone to chatter in cornering (something a Cadillac owner wouldn't want). The additive is to smooth out the chatter.

There are also lockers, which do NOT have limit slip action, they are locked together, or full unlocked. They don't work necessarily smoothly like the limited slips (best for off road use and maybe track use).



Only add the additive if you need it. If you see no chatter, don't worry about it.

Raider1v1
04-18-07, 02:45 PM
yah but in the service manual it says "this is not a positive locking differential" and when its on jackstands and i spin one wheel, the other spins the other way. so thats why i was thinking its just a regular open diff.

quote from the 69 service manual "this unit is not a positive lock type"

N0DIH
04-18-07, 02:55 PM
GM designs around a 10yr/220K mile expected vehicle lifespan. Most of these cars are just at this based on time, but not miles. The hard parts should be just fine.

These axles should not be anywhere clsoe to wearing out at 200K miles. The trucks, and the axles are only a very small amount larger than the cars. And the 71-76 B/C/D cars and 77-89 B/D cars never saw this issue. The common denominator is the gasket. Trucks never got the wrong gasket, only the 90-96 cars.

The Ape Man
04-18-07, 07:01 PM
GM designs around a 10yr/220K mile expected vehicle lifespan. Most of these cars are just at this based on time, but not miles. The hard parts should be just fine.

These axles should not be anywhere clsoe to wearing out at 200K miles. The trucks, and the axles are only a very small amount larger than the cars. And the 71-76 B/C/D cars and 77-89 B/D cars never saw this issue. The common denominator is the gasket. Trucks never got the wrong gasket, only the 90-96 cars.

Worn axle shafts were a very common problem with '77 and up RWD Cadillacs. I've personally repaired several dozen including 3 in my current collection. You are leaving out surface hardening when comparing axles. My fleet friends tell me that those extra holes that you guys think are there for oil are actually used as assembly fixtures in the factory.

The Ape Man
04-18-07, 07:08 PM
yah but in the service manual it says "this is not a positive locking differential" and when its on jackstands and i spin one wheel, the other spins the other way. so thats why i was thinking its just a regular open diff.

quote from the 69 service manual "this unit is not a positive lock type"

Sounds like a regular garden variety open differential. The posi (or whatever you call it) Will only spin the opposite side tire with the driveshaft locked if it's really worn out. I've seen some really worn out stuff but cant remember seeing one that bad.

Brother_B
04-18-07, 08:11 PM
yah but in the service manual it says "this is not a positive locking differential" and when its on jackstands and i spin one wheel, the other spins the other way. so thats why i was thinking its just a regular open diff.

quote from the 69 service manual "this unit is not a positive lock type"

Your quote is right in the section about Controlled Diff. It says to use the special stuff for the Controlled Diff. Your manual also tells you how to identify whether or not you have the Controlled Diff. The letter "G" precedes the number stamped on on the front face of the carrier assembly for a CD.

JTraik
04-18-07, 08:19 PM
It is very easy to tell if the differential in your '69 is indeed controlled or not. If it IS controlled then there is a little aluminum ring or tag that goes around the fill plug, if the differential is not controlled then there is no tag or ring....

Raider1v1
04-19-07, 08:32 AM
well i was talking to the mechanic about it yesterday, and he told me about the g-2 stamp. i didnt know about the tag/ring though. thats handy!

what i just needed to know was about the fluid. he said that what controlled was, was a limited slip type diff. so if it was i needed the 80w90 gear oil and a bottle of conditioner additive. is that right?

and then, obviously if its just a plain one, get a regular bottle of 90w oil and change it out :)

N0DIH
04-19-07, 09:34 AM
I can see the combo of the 2, hardening the axles might be part of it, but I don't think it is all of it. I guess it would be key to find people who have replaced the gasket early on and kept the factory axles and see long term if the axles wore at all like without the right gasket.


Worn axle shafts were a very common problem with '77 and up RWD Cadillacs. I've personally repaired several dozen including 3 in my current collection. You are leaving out surface hardening when comparing axles. My fleet friends tell me that those extra holes that you guys think are there for oil are actually used as assembly fixtures in the factory.

Timothy60
04-19-07, 10:04 AM
I agree. It would be at the very least interesting to be able to survey Fleetwood owners concerning the correlation between gasket replacement (or not) and axle problems. But I would suspect that most current Fleewood owners did not purchase their vehicles new thus they would have limited or incomplete knowledge about its service history. That would confound the statistical validity of the survey but it might reveal some informative (albeit non-scientific) patterns about this assembly.

rlyons
04-19-07, 01:47 PM
If the holes are not for oil then why does the cover have channels pressed into them funneling oil to the holes and why are all aftermarket gaskets made with the holes? I vote for the passage of oil and yes they may use the holes for holding the assy in manufacturing but that doesn't mean they are not also for oil passage.

N0DIH
04-19-07, 02:07 PM
Yes, the might be "transfer lugs" for fixturing, but they are also the oil feeds to the axle tubes.

Else the cover would not be designed that way. Look at the 12bolt too, it is even more evident. And the 8.2" that this axle was based on.

http://i159.photobucket.com/albums/t142/mompower/12boltaxle.jpg

Look at the cover, the 10 bolt is similar but the features are on the inside, the 12bolt, very pro-nounced on the outside.

The Ape Man
04-19-07, 06:53 PM
Sorry but I don't buy it. If the axle assembly is properly filled there is already oil at the bearings. The level rises with the vehicle moving. If you drive one of these cars with a neglected bearing failure and the thing catches on fire you get to see just how good the oil supply is. When servicing a full (of oil) axle on level ground oil comes out the axle tubes. If oil at the bearings was the goal then why have those holes lead back near the center of the axle housing ?? ?? ?? Seems like a lot more oil could be supplied if they had some tubes leading right to the bearings. A few press fit steel pipes could be fitted easily. If anything that dimple is there to feed oil back to the ring gear support bearings. The 12 bolt was designed to take serious torque multiplied 4 times. The ring gear bearings take a whole lot more punishment than axle bearings under load. My 2.21 posi has many of the same guts as that 12 bolt and no dimples in or out. Like I already said the same principal used on Muncie 465 transmission input shafts could be applied to axles in reverse fashion to supply plenty of oil to axle bearings.

N0DIH
04-19-07, 11:02 PM
If you are talking the 77-84 8 3/4" rear is is not the 12 bolt and shares nothing from it. It is the Pontiac "P" axle that came from the 71-76 B/C/D cars, only they shrunk the ring gear from 8.875" to 8.75", as power from the 425 wasn't gonna hurt that gear and it might boost fuel economy slightly. And is only a 10 bolt. Grab your FSM and read about it, I believe it talks about it. I'll grab my 76 book and see what it says.

cadillacmike68
04-21-07, 11:36 PM
You obviously have NEVER looked that close. AND you haven't had one fail, like mine. These axles should last well over 300K, even to 400K with NO issues. They do NOT. The trucks have always had the RIGHT gasket and have NO FAILURES. The B/D cars have had massive failures

What part does everyone just not understand?? GM even admits this to the commercial segement, limo/cop cars/taxis. So why is it so darn difficult to understand that this is a REAL PROBLEM?????????????????

7.5" axles, not an issue, OEM used gasket goo
8.5" axles, ISSUE.
9.5" axles, not an issue, they got the right gasket.

I will dig up my picts and show you the damage.

Look at the pictures of the rear axle housing on the first page of this thread. (http://www.cadillacforums.com/forums/rwd-19xx-1985-deville-fleetwood-1985/102320-differential-dilemma.html) (http://www.cadillacforums.com/forums/rwd-19xx-1985-deville-fleetwood-1985/102320-differential-dilemma.html%29). Is it that hard to see???

Sorry, I am fed up with people who have never pulled their own axles to look and to think that gear oil is a lifetime lube. It is NOT. GM specs this to be changed around 50K miles. It is one of the most neglected maint items.

as chris tucker said in rush hour "I cannot believe this sh!t"

How do we tell what size axle we have?? I have the two volume service manual at home. I can look up the option codes in the trunk as well - when I get home. Was the 8.5" the most commone one (please say no)??

I have had my rear axle oil changed a coupe of times, but they didn't mention anything about the gasket being wrong when it was done. I wonder why???

JTraik
04-22-07, 08:12 AM
Sorry but I don't buy it. If the axle assembly is properly filled there is already oil at the bearings. The level rises with the vehicle moving.

Correct, but the level rises due to those holes. As the ring gear is moving forward with the car, it effectivley acts as a pump by sucking the oil back towards the cover and sprays oil to the pinion bearings. By sucking it back towards the cover the level rises above the holes and pours into the tubes, the uneven pressure in the tube is then forced out through the carrier bearings... its a wonderful cylcle. This is precisely why you fill the housing over half way up the ring gear, when in motion the oil level in the main housings dips down to where the ring gear is merely dipping itself into the oil pool below.... thats really all the oil that it needs.


If oil at the bearings was the goal then why have those holes lead back near the center of the axle housing ?? ?? ?? Seems like a lot more oil could be supplied if they had some tubes leading right to the bearings. A few press fit steel pipes could be fitted easily. If anything that dimple is there to feed oil back to the ring gear support bearings.

Well technically they would do the same job and it is much cheaper and easier to just stamp out a hole in a tube rather than channeling.

The Ape Man
04-22-07, 09:36 AM
If you are talking the 77-84 8 3/4" rear is is not the 12 bolt and shares nothing from it. It is the Pontiac "P" axle that came from the 71-76 B/C/D cars, only they shrunk the ring gear from 8.875" to 8.75", as power from the 425 wasn't gonna hurt that gear and it might boost fuel economy slightly. And is only a 10 bolt. Grab your FSM and read about it, I believe it talks about it. I'll grab my 76 book and see what it says.


There are at least 2 different rear axles used from '77 to '85 RWD Cadillacs.
The ones used on the 77,8,9 were also used as heavy duty units later on but not seen much. The 2.21 posi unit out in my garage on vacation is an 8-7/8" ring gear. These units weigh at least 20 lbs more than a typical HT-4100 powered car's axle. Funny but the parts books show the 8-3/4" and 8-7/8" internals as being the same parts numbers.
BTW every one of these axles got gouged with old age. Usually happened way over 100,000 miles and these were the first years where cars regularly gave service that long. '76 and before seemed to have planned rustolescence mastered. Axle saver bearing kit to the rescue. A set of new axles from the dealer were 300 bux back in the early 80s.

The Ape Man
04-22-07, 09:43 AM
Correct, but the level rises due to those holes. As the ring gear is moving forward with the car, it effectivley acts as a pump by sucking the oil back towards the cover and sprays oil to the pinion bearings. By sucking it back towards the cover the level rises above the holes and pours into the tubes, the uneven pressure in the tube is then forced out through the carrier bearings... its a wonderful cylcle. This is precisely why you fill the housing over half way up the ring gear, when in motion the oil level in the main housings dips down to where the ring gear is merely dipping itself into the oil pool below.... thats really all the oil that it needs.



Well technically they would do the same job and it is much cheaper and easier to just stamp out a hole in a tube rather than channeling.

Ray
Charles could have seen that.


If there is extra oil level and pressure against the rear cover and magic hole inlet then there must be a lack of pressure and level somewhere. That somewhere would pretty have to be at least 10 times closer to the hole's outlet than the axle bearings. If you were a drop of gear oil would you flow towards a low level and vacuum or would you travel 10 times further in the opposite direction to save an axle bearing in distress?

cadillacmike68
04-22-07, 12:00 PM
So, are all of our beloved 93-96 Fleetwoods FUBAR'd or what ?? :want:

inquiring minds want to know.:gnome: :brutal:

Now I have to get home and dig out my options code dechpherer and manual and try to figure out which axle / ring gear i have and possibly take off the rear cover - there's another oil spill for the driveway this will result in:
my wife ===> :thepan: <=== me

N0DIH
04-22-07, 09:15 PM
ALL 93-96 Fleetwoods with that aren't limo's have the 8.5". The 9.5" is reserved for limos.

You CAN always upgrade any 77-96 B/D body to a limo 9.5", but no 9.5" came with the hardware to make the ABS/TC work.

I have installed a 9.5" in my 96 Suburban, it is an excellent rear end, very very tough, puts the 8.5" to shame. But, it is HEAVY, far heavier than the 8.5". If I ever get into towing consistently with the car, I will probably go with the 9.5" and try to adapt the Impala SS discs and the Fleetwood ABS/TC to it. Bit that is for another day....

cadillacmike68
05-10-07, 11:18 PM
Ok, I read this entire thread twice now and some of you guys are smoking too much ganja. :thumbsup:

I'm back home and went through the SM. :yawn:

First, off, there was no 7.5" ring gear in the 93-96 Fleetwoods and the 9.5" did not use a gasket, it used RTV sealant. If you don't have an armoured body and / or coachbuilder chassis, then you have an 8.5" ring gear.

Next, I can see the two holes in the nice big photo, but i also notice that they are for the most part, INSIDE ths area where the gasket would go, drawings in the 1995 Fleetwood Service Manual confirm this.

Next, I bought a gasket from the Cadillac dealer here in Tampa, Its a recently revised PN and it DOESN'T have holes / slots for these two assembly holes. It's also only 1/3 - 3/8" wide and will not cover up more than 30-40% of these holes.

Next, the axle fill level, which according to the SM states should be at the fill plug level to no more than 15mm below, will allow plenty of gear oil to the axle shafts and outer ends where the bearings are with or without these holes being plugged, of which they cannot be more than 30-40% blocked anyway. These guys sold a LOT of Fleetwoods, and they have NEVER seen an axle failure on the 93-96 Fleetwoods. I then checked with a Chevrolet dealer, same thing, the holes are for assembly fitting and not the primary oil passages for the axles and they haven't seen any axle failures on Caprices either. The linked article cites fleet usage, likely for police, taxi usage, which is beating on a car like there never was. Those things - its a wonder they are still running after 5 years. :eek:

There must be another proximate cause of the failure in your axles, N0DIH. You are probably beating on your car. It ain't a Trans Am. You whip it around corners, and it'll do this eventually. How many miles do you get on a set of tires?? :confused:

And weak axles aren't soley a fault of GM, My brother wore out a pair of T-bird axles. I think it was a 1986, but he was never nice to his cars either, he trashed a 1970 Fleetwood 75 Sedan back in the 80's, one of only 900 built. :thepan:

I had my car's axle flushed back in 2001 or 2002. They most likely changed out the gasket then, but in my determination, it doesn't matter. Time to have it done again, but there is some tubing blocking access to the upper bolts of the diff cover. How does one get access to the top bolts?

Don't beat on your car and it will last longer :tisk:

N0DIH
05-11-07, 10:44 AM
No, no beating. Explain why my 80 Trans AM has never had an issue? That car gets run MUCH harder. I have NEVER seen a 70-81 F-Body with a failed axle shaft. Broken maybe, but not this issue. I drive lots and lots of highway and some city miles. Mainly 80 miles out of every 120 daily is 65-75 mph. The rest is 30-60 mph, some stop and go, not a rough drive at all, annoying, but not rough on the car at all.

In the HT4100 and 307 cars the 7.5" axle was standard. So yes, it saw the same use as the 8.5"s. Even the L99 cars from 94-96 got 7.5" axles, again, never once heard reports of any issues. But the 8.5", yes.

9.5"s were reserved for limo's, so no you won't find one. And no, I don't recommend one unless you are going to tow heavy often, else, the weight of the axle is NOT welcome. Trust me, I put one in my 96 Burb in place of the 8.5", it was quite noticeablely heavier. I didn't like that, but I did like the beefyness of it.

I can pull my 96 Burb axle shafts out if you like, 235K miles, with the right gasket. No appreciable wear. My 94 Fleetwood with wrong gasket, significant wear. Yes, the burb axle is slightly larger bearing, but not enough to have virtually no wear.

I get 50K+ to a set of tires, if not more (on a 40K mile rated set). I like to corner, but I don't push this car, don't need to and don't get the opportunities too.

Yes, there is a chance that heat treating wasn't done properly or at all on them, so the surface wasn't hard enough to wear properly, but I can't see that the 8.5" missed it and the 7.5" did.

Fleets saw massive failures of these axles by 30K to 70K miles. IIRC a TSB was issued to the commercial side, 9C1, 9C6 and Limo fleets. Not to general consumers. Again, GM admitted the problem. Is it that hard to understand?

Better yet, go the dealer and order a gasket, does it come WITH out WITHOUT holes? Why would the trucks get a different gasket with the holes factory with the exact same axle center section? Different axle manufacturer I would bet. And I would bet GM never carrierd the wrong gasket in dealer inventory.

Timothy60
05-11-07, 12:38 PM
Nodih, I seem to remember a few weeks ago in one of your posts about the bearing seal on your Fleetwood leaking . . . didn't you have trouble with a broken pinion lock, too?

Timothy60
05-11-07, 01:06 PM
Again, this is my view after reading this thread a number of times: I suspect (although I can't corroborate this statistically) that most failures concerning the 8.5 axle transpire under heavy bearing load conditions such as sustained high-speed operation, trailer towage, or chronic abuse. That may be why fleet/police applications of this typically durable axle assembly have been particularly vulnerable to outer bearing/seal failure: extreme operational loads amplify a problem that may never surface for the average Fleetwood owner." The recent post by CadillacMike 68 seems to make a lot of sense in this direction, too, if I understand his point correctly.

Old Fleetwood
05-11-07, 04:05 PM
The bottom line for me:
Since I DO tow, I plan to pull the diff. cover, drain and refill the diff and then have the proper gasket (thick, not thin and cheap) installed so that the holes are not obscured - JUST IN CASE.
Yeah, it may be a "belt and suspenders" type of thinking, but I can not bring myself to believe that holes that big would be merely for assembly line movement. Sure, lube will slosh around with car movement, and also by the movement of the ring and pinion, but the holes are FAR too big for an assembly line pin or trolley.

N0DIH
05-11-07, 07:20 PM
I can see them for "transfer lugs" as they are often called, but they also do the extra duty, else why would the rear cover have the shape to funnel oil there? Just looks?

cadillacmike68
05-11-07, 10:11 PM
I DID buy a gasket, new PN from GM. It doesn't have slots / holes, but it WON'T cover more than 30%, if that, of the holes we are talking about. And I may trim that part myself before installing it, IF I can get to the top few bolts on the diff cover - there's some metal tubing up there getting in the way...:mad:

cadillacmike68
05-11-07, 10:16 PM
Remember, that the F- bodies are over 1,000 lbs lighter than the D body Fleetwoods. You stated that you like to corner - how hard??? that can be a large stress on the axles. I leave the hard cornering to my wife's CTS. :thumbsup:

I do tow (a boat). That's why I had the axle serviced back in 01 or 02, and will get it done again (or will do it myself if i can get the cover off.

Do I need to use gasket sealer on the gasket????

N0DIH
05-11-07, 10:59 PM
Gasket maker (Ultra Black, Blue, Copper, Grey) OR a gasket, but not both.

What is the P/N you got? Who was the supplier of the gasket?

Corner hard? No, not often, on occaision, but not often at all. Like I said, no real places to do it, and the car is too heavy to really do like my T/A can.

My T/A weighed in at 4030 lbs on a real scale, the Cad is said to weigh 4400 lbs according to Cadillac documentation. So hardly 1000 lbs. That is only 100 lbs per wheel. Not much diff at all.

If you take the top bolt off then push the e-brake cable up out of the way. It is a fairly stiff cable, but you shouldn't have any real problems moving it.

rlyons
05-11-07, 11:08 PM
Just put the gasket on it with the holes or cut your own and then there is no worry, it is not worth arguing over. If you want to leave a gasket on yours with no holes then do it, end of story. It is your car and you have a right to do either. I personaly put on a new gasket with holes and I will change the oil every year just like I do on my truck with 225,000 miles on the original engine, transmission and rear end.

N0DIH
05-23-07, 11:09 PM
According to Bill Harper (Navy Lifer):
The history of this gasket: it was PN 3984820 until 1985, became PN 3993593 until 1989, then PN 26016662 (as used in production for all B-bodies) until April 1999, when it became PN 26066456, which is NOW superceded by PN 15807693 as of the 2007 model year.

cadillacmike68
05-24-07, 09:59 PM
Mine that i just bought is PN 1580-7693 - same as M0DIH's reference above. It DOESN"T have hole cutouts, but it WON'T block the holes either! :thumbsup:

N0DIH
05-26-07, 09:17 PM
What is the quality of the gasket? Cork? Paper?

I really like the NAPA Premium gasket, that is a nice one, very nice quality and design. Harder to find, most stores won't carry it, $10 price tag....

cadillacmike68
05-26-07, 10:32 PM
The MATERIAL is heavy paper. The QUALITY looks acceptable for its intended purpose. I have no idea who made it. It's in a GM clear plactis sealed bak with a cardboard backer.

I don't like cork gaskets, one 1/4 turn too much and you compress it and it leaks forever.

N0DIH
05-26-07, 11:36 PM
The NAPA one is a metal reinforced cork, almost impossible to mess it up, and I have reused it 2x now with not so much as dampness....

cadillacmike68
05-29-07, 10:07 PM
That's a new twist on the gasket material (notice i said material - not quality).

I don't plan on getting under my car to change out this axle fluid more than once every three years. In fact I'm avoiding it right now, I don't want another mess in my driveway :crybaby:

The Ape Man
05-30-07, 07:07 PM
My gear oil is 27 years old. Been through 5 presidents. It ain't broke....

C66 Racing
06-04-07, 12:09 AM
Thanks for the advice. OK, I'm convinced. I'll change the differential lubricant the next time I change the oil. Maybe Amsoil has a lubricant designed for differentials so I'll look into that since that's what I have in the tranny with good results.

I know I'm catching this thread way late, but I've been offline for the past three months. Though this may have been answered above, I thought I'd give you the exact link to the right product for your diff.

AMSOIL does make a very good differential fluid and which they recommend for the Fleetwood differential:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (http://www.c66racing-synthetics.com/Product%20Bulletins/SVGPB.htm)

This is the same fluid I've been using in my 2002 Corvette Z06 on the track since the 2004 season (no failures) and that I'll be putting in my 06 CTS-V next weekend.

Note that this fluid comes with friction modifier already added and adding extra additive is not normally required (I don't use any in my Vette). But, for those whose differentials chatter, AMSOIL does offer this friction modifier:
AMSOIL Slip-Lock Differential Additive (http://www.c66racing-synthetics.com/Product%20Bulletins/ADAPB.htm)
:cheers: