: Today's Educational Pictures: Inside Your Differential



Cadillac Tony
07-07-08, 01:08 PM
After listening to the really annoying whine my diff has developed lately (road trip for the 4th of July), my Techs decided it was time to replace the clutch packs in my rear diff.

Contrary to popular belief, there is no need to replace the entire rear differential to fix the whine. The cause is worn clutch packs, so you folks who are out of warranty and want to DIY - keep this in mind. Even if you pay the Dealer out of pocket, there's no need to replace the whole unit unless it's trashed. As everyone's mileage increases and warranties start to run out, I figured this info would be useful to some people here. Everything inside the diff (the case, ring gear, pinion, etc) looked great, it's just that little stack of clutch plates that cause all the singing.

I didn't have time to document an entire step-by-step of the removal since he zipped it out in 10 minutes while I was chatting with a Customer, but here's some pictures of the inside of the case, the guts, and the culprit of the whine: The stack of worn clutch packs.

Fun pictures for those who enjoy staring at machine guts just to satisy your curiosity about what's inside. Click for a larger view, and enjoy.

Crown Vic Owner
07-07-08, 01:36 PM
How much are those set of clutch packs? Just wondering.

Cadillac Tony
07-07-08, 01:41 PM
Normal retail price on the clutch plate kit is $145.80 (x2), and the axle seals are $20.43 (x2), so about $335 for all the parts needed. Beats $3,000 for a whole new rear, eh? :D

Crown Vic Owner
07-07-08, 01:45 PM
Is it difficult as far as setting the mesh? Is it possible to change the RAR in these diffs (do they make the gear sets)?

TGrits10
07-07-08, 02:12 PM
Is it possible to change the RAR in these diffs (do they make the gear sets)?

Last week I saw mention of the standard cts 3.42 gears dropping right in with only one minor modification, see if you can search it up.

CTSV_Rob
07-07-08, 02:20 PM
Great stuff Tony, Always like to see inside to see how it works.

How often did you change your Diff fluid and how many miles do you have on the Diff? I am just curious because I am changing the fluid about every 6 - 7K which may be over kill but I don't want to take any chances. If you did the same and have low miles then it might not be worth my effort. If you just drove it until it died then I will continue to do it and see if I can go a little longer before the dreaded whine.

17K on mine and she is still quiet.

Twitch
07-07-08, 02:36 PM
Mine may be getting louder. I wonder if the dealer would change just the plates, or put a new diff in? I only ask cuz, if my diff has been good so far, why change it.
BTW Do we know if the replacement diffs are new or rebilt?

Great post

Cadillac Tony
07-07-08, 02:57 PM
Rob,
I'd say keep doing what you're doing. Most whines are caused by fluid loss out the vent, which is why GM released the TSB about adding a hose to the vent to keep the fluid in. The clutches slip on each other in tight turns, and dirty or low fluid will only accelerate the wear.

Twitch,
The Dealer would probably be happy to do so, just make sure they have a good heavy line man to do the job (a lot of techs these days are just "parts changers"). The Dealership's warranty cost is 1/5th of a diff, plus the Tech gets paid more for a rebuild than a replacement, so it's a win/win/win for you, the Dealer and Cadillac.

the cadillac kid
07-07-08, 03:30 PM
great info as always, Cadillac Tony. :thumbsup:
hope i never have to use it though :D

rand49er
07-07-08, 03:40 PM
... I didn't have time to document an entire step-by-step of the removal since he zipped it out in 10 minutes while I was chatting with a Customer ...Well, we know where YOUR priorities are!

J/k, Tony, nice to see info like this here. :thumbsup:

Ques: So, you had the seals and the clutch pack changed and put in new fluid, of course ... did the whine go away? I mean, that alone did indeed fix it?

Civardi
07-07-08, 03:40 PM
Thanks for this one. I bought mine w/o a warranty knowing all the issues but so far so good. Plus mine had the carrier replaced in 12/05 with and 06/07 diff so I feel a little better.

Cadillac Tony
07-07-08, 03:58 PM
... did the whine go away? I mean, that alone did indeed fix it?


Not 100%. There's still a little whine, but it was starting to bind on tight turns (like backing out of the driveway and cutting the wheel) as well, so I had it done in hopes it would fix both. The binding is gone 100%, but there's still a small amount of whine. It's definitely diminshed though.

I wouldn't suggest having this repair done solely for whine. The clutches binding on turns (what GM calls "parking lot maneuvers") is indicative of either insufficient lubrication or wear. If draining and refilling with the proper fluid doesn't fix it, this would be the next step. I should have been more clear in the first post, but the main reason I did this was the chatter on tight turns- I'd been putting off opening the diff case, and the whine just pushed me over the edge. :)

ctsv154
07-07-08, 04:15 PM
I just replaced the pinion seal on my car. Is there anything special I should note on the pinion nut? How many lbs should it be at?

thanks

Twitch
07-07-08, 04:57 PM
Hey Tony, why dont you bump this thread every month or so. Give us some updates. This information may become very valuable to a lot of us. :thumbsup:

StealthV
07-07-08, 05:28 PM
Driving in a straight line, the clutch packs are pretty much doing nothing so I'm struggling to see how its connected to directly solving the whine problem.

Chattering and binding during parking lot turning manuevers and gear whine are not the same thing. Which one are we talking about here?

http://www.summitracing.com/streetandstrip/images/v4_professOD_blue.gif

NormV
07-07-08, 05:54 PM
How many miles and your typical driving style? GM fluid?


Thanks,
Norm

Cadillac Tony
07-07-08, 06:11 PM
Chattering and binding during parking lot turning manuevers and gear whine are not the same thing. Which one are we talking about here?



I just went back and re-read my first post, and I seem to have typed "whine" at one part that I intended to write "clunk". Sorry about that.

The reason I had them open it up was to correct the binding on tight turns. It's been doing it a while and I've been avoiding opening the diff, but the whining drove me nuts this weekend so I talked to my shop foreman. He told me that some of the whine is caused by reduced thickness in the clutch plates, which introduces a certain amount of play in several components inside the diff. I don't profess to have as much knowledge of the inner workings of a differential as I do an engine, so if you're looking for a more detailed explanation I'm out. :lol:

I'll talk to him in the morning and see if I can get some more detailed information. He did mention something about a pin being partially slid out of place inside the carrier when he opened it up - I'll follow up on that and learn more.

Norm,

About 17k miles on this diff, GM fluid with additive. Driving style can be considered "spirited"- no clutch dumps or wheelhopping, but I will stand on it in 3rd to pass someone and do the occasional run up to 100. I don't beat on it, but don't baby it either.

TGrits10
07-07-08, 06:58 PM
I just went back and re-read my first post, and I seem to have typed "whine" at one part that I intended to write "clunk". Sorry about that.

The reason I had them open it up was to correct the binding on tight turns. It's been doing it a while and I've been avoiding opening the diff, but the whining drove me nuts this weekend so I talked to my shop foreman. He told me that some of the whine is caused by reduced thickness in the clutch plates, which introduces a certain amount of play in several components inside the diff. I don't profess to have as much knowledge of the inner workings of a differential as I do an engine, so if you're looking for a more detailed explanation I'm out. :lol:


The wear allowing play and contributing to clunking makes some sense, but.... I'm still confused whether you're talking about clunking or whining :confused:

Cadillac Tony
07-07-08, 07:04 PM
Let me see if I can make it any clearer:

-I had a clunk/bind noise on tight turns.
-I didn't feel like having them install another rear end, so I lived with it.
-Now it started whining too, so I talked to the shop foreman.
-He said replacing the clutch packs would eliminate the binding on tight turns, as well as some of the whine.
-I had the work done.
-It no longer binds on turns, and the whine is reduced.

To avoid any other confusion, I am not referring to the clunk caused by pressing the clutch pedal at low speed or releasing it at high speed- that is caused by the front bushing on the differential. The clunk I had was a binding or shudder when making an extremely tight turn, like a U-Turn, which was caused by the clutch packs in the differential.

Black Sunshine
07-07-08, 09:26 PM
I had a grinding sound (could tell it was hanging) from the rear during slow parking lot turns and a gradually louder whine while running on the highway. Around 30K on the odo.

My home dealership is also a GMC truck dealer. Their heavy-line mechanic rebuilt my rear under warranty. I can't confirm but the mechanic assured me he did a lil research with GM Performance and ordered in some upgraded parts. Haven't heard a single sound in close to 45K miles.

v-sam
07-07-08, 10:58 PM
I get clunk just from engaging the cruise control i.e. getting on the throttle or letting off the clunk comes from the rear end.

Cadillac Tony
07-07-08, 11:16 PM
^ That's the front diff bushing.

trukk
07-08-08, 04:22 PM
^ That's the front diff bushing.
^^ It's also caused by worm engine mounts, dual mass flywheel, and worn prop shaft bearing. Like Tony said though, front diff bushing is the number one cause.

-Chris