: Rear end- Important information

02-11-05, 12:42 PM
Found this PI and I dont remember it ever being posted...

If you have a new car, break in the rear end right... and if the dealer installs a new rear end, BREAK IT IN AS WELL.

500 miles is the breakin:

03-05 Cadillac CTS , CTS-V and SRX Howl Whine Noise from Rear Axle - kw accelerate decelerate #PIP3051 - (07/08/2004)
03-05 Cadillac CTS, CTS-V and SRX Howl Whine Noise from Rear Axle

Howl or whine noise from the rear axle on accel and/or decel. Most noticeable at speeds between 35-50 mph.

Compare the noise to another identically equipped vehicle with similar mileage and make any necessary repairs. Axle break in procedures must be strictly adhered to during initial break-in as outlined in the Owners Manual. This also applies to any replacement axles that would be installed in a customer's vehicle. For 500 miles, it is suggested that rapid acceleration be avoided, as well as to avoid driving at the same speed for more than five or ten minutes at a time. The vehicle should also not be used for towing during the break-in process.

(03-05 Cadillac CTS) and (04-05 Cadillac CTS-V) and (04-05 Cadillac SRX)

Just a reminder... Its really hard for me to not launch for 500 miles so we all need to be careful when we get new rear ends.


02-12-05, 11:27 AM
And then change the fluid.

02-12-05, 11:42 AM
Reed -

The 2nd rear end in my V was without a doubt broke in entirely perfectly. I am the only one that drove the vehicle after it was picked up at the dealership (though the dealer had put about 50 miles on it "testdriving"). I did not change the fluid and regret not doing so as I think this is the primary area of concern.

Regardless, for the first 1,000 miles I has very easy and for the first 600 I babied the car without ever, not one application of full throttle and zero hard launches. I figured since it took them nearly 3 weeks to get a diff on hand and get the car back to me, I didn't want to go through it again.

And still it begin making serious whining about 2,000 miles after replacement - same as the factory diff did...so what gives?

carpe dm
02-12-05, 12:29 PM
Reed -
And still it begin making serious whining about 2,000 miles after replacement - same as the factory diff did...so what gives? What is your current condition? Does it still "whine", or has it smoothed out? :hmm: You might try Amsoil diff lube, and/or Mobil 1 along with the GM LS additive. Hope it is OK.

02-12-05, 01:25 PM
My diff is currently jacked and in need of replacement, due to the fact that the limited slip has basically become a sort of mini spool. There is supposed to be a regional rep in the area early this week to look at it. Until then, I'm driving her as little as possible. The whine is a howl, and the chatter is now a scream when performing low speed parking lot style turns. Basically, what I am hearing is the tire on the inside of the turn chirp away since the diff isn't allowing any "differential" action.

Carpe dm -

I know what gives, the question was more rhetorical really. I know that this time when the diff is replaced I will INSIST on the additive (which they refused to use before) and I will INSIST that they swap the fluid at 500 miles and then I will PERSONALLY switch at 1000 miles to something like Amsoil or Mobil 1 to guarantee the longest diff life possible.

The Magnacharger wouldn't want it any other way :burn:

02-12-05, 02:20 PM
i'm beginning to think that this is cadillac's way of blaming the owners for the failure of their car's rear diff

02-12-05, 05:53 PM
I may have missed this but....

Does anyone have first-hand experience that switching to Amsoil or Mobil-1 is a good thing?

Has this been established with Vettes or V's?

The only reason that I ask is that Supra Twin Turbo's (my last car) had similar, albeit milder, "noise" problems with their Getrag 6-spd and sometimes diff.

Lot's of guys went to Redline and/or Amsoil.

Turned out to be a big mistake -- the *only* correct solution was frequent fluid changing using the special/expensive Toyota fluid.

I realize that these are different systems, but the "tone" of the discussion here is identical to that on the Supra boards 5 years ago....


02-12-05, 06:55 PM
If you buy a rear from a performance tuner (example DTE for a vette) it comes with Redline and the GM additive and a warranty! They supply the lube and stand behind the unit, must be something to the combination :rolleyes:

02-12-05, 08:22 PM
Just changed the rear end oil in the V @ 1100 miles, repaced the Diff lube from GM, and used Redline MT90. Car still has whine under accleration between 40-80 MPH. No problems with the rear yet, leaking, grinding etc. Just whines once the the fluid is warm, usually takes about 20 - 30 miutes of driving.

02-12-05, 09:12 PM
FYI guys. From Phil at dynotech.

Hi Marty,

We are indeed aware of the inherent failures of the Cadillac CTS-V differential and we do intend to do *something* about it. We don't have a donor core here to use for development however and that is the main reason why we haven't done anything to date. We've looked all-around for one, but it seems GM is taking all the old, damaged units back and you can't buy one new either due to them being on backorder from the manufacturer.

If you, or someone else can get their hands on a complete, un-broken unit that we could borrow for awhile for development purposes, we would be very interested in looking at it to engineer a solution to the current problems everyone is having with the stockers.

BTW- RSG copies and uses a LOT of our designs and components for the C5 Corvette differential, so they certainly are NOT doing anything that we haven't tried or done a LONGGG time ago...:annoyed:

02-12-05, 09:19 PM
"We've looked all-around for one, but it seems GM is taking all the old, damaged units back and you can't buy one new either due to them being on backorder from the manufacturer."

And yet Cadillac/GM claims to know nothing of any rear end problems :hmm:

02-13-05, 08:55 AM
I am told the 06 V owners manual will have specific language about the rear end, and the break in period. The absence of this was considered a large oversight.

I was also informed the M class BMW's have this language there so the manufacturer can point to it when you smoke your rear end. I am not into the Beemers so I will let someone else validate that.

This is concerning me, since it appears as though the general is going to look for a way around this, rather than re-engineer the rear for both the wheel hop and the inability to hold up to the punishment that a rear with 400+ horspower is going to take...

02-13-05, 10:57 AM
My concern is that specific language will not solve the problem. I broke my V in 99% properly for the first 500 miles (not just for the rearend's sake) and then again broke in the replacement rearend for 500+miles in an even easier fashion than the first.

Words on paper are not going to fix a mechanical issue - General!

Here are the items that I believe may have contributed to the current rear end failure:

1) Dealer drove the V for some 50+ miles after install - who knows how hard they drove it.
2) Dealer did not include the limited slip additive
3) When I received the car back, several bolts (cradle bolts to name some) were not properly torqued. Could things have been rocking around more than they should have been? I did not discover this until the BMR AWH kit was installed after the new diff was broke in.
4) Dealer would not swap out the diff fluid at 500-1000 miles after installation though I requested such. Though I could/should have done this myself, since I was aware the l.s. additive was missing, I wanted to keep it in the dealer's hands (i.e. don't let them claim my swapping of the fluid voided warranty, etc.)
5) The LS6 power output is too great for the differential - and the wheel hop when it occurs only makes this worse.
6) Once everything was broke in and seemed to be good - I DO IN FACT drive the vehicle like I believe Cadillac engineers intended it to be driven (videos from their website as evidence). I do not drag race, but like the twisties more than any straight line stuff. This should not have any affect on the rear differential as these are events that all occur once the vehicle is in motion.

No amount of verbage is going to solve the problem that at least I've experienced with the rear differential. I don't think that even a 2,000 mile break in would resolve it. Torque management in 1st and 2nd gears to <325 ft lbs? Maybe...but then the 0-60 would be what - 6 seconds plus?

I'm hoping that a solution, other than "break it in really, really easy and then change the fluids after that period" is found. For those of us who already own V's, a change to a future model owner's manual does absolutely nothing to help us :annoyed:

Also, don't forget that it isn't just the 400hp V's having rear end failures, other lesser powered Cadillac models are having them as well.

02-13-05, 12:01 PM
My V has 8,000+ miles on the original diff and it was not broken-in "correctly." Immediately after driving the new V off the dealer lot it was subjected to 7 hours of constant high speed interstate driving (70+ mph) as well as many full throttle romps down the on-ramps.

Seems those who are gentle with their diffs during the break-in period have the greatest chance of repeat failure. :hmm:

If the limited slip additive was not used at a fluid change, the carbon fiber clutch packs inside the diff wear themselves out. This wear puts millions of tiny, nearly hard as diamond, razor sharp carbon fiber particles in the diff fluid. These particles will quickly eat away the gears and bearings.

02-13-05, 12:19 PM
Ahh...Rick. You subscribe to the "break it in fast and it will run fast" principle, as I have with any engines I've built, or motorcycles I've owned.

For some reason I tried to be pretty nice on the original diff, and really, really nice for diff number 2. I am sure you're right about the limited slip additive and the carbon clutch packs destroying my current diff. I've tried to make this point time and again with the service manager without success.

They claim that when they drained the fluid and added the diff additive to the replacement fluid <1000 miles ago, that the old fluid "...looked great, almost like new..." which I know is total bull$hit.

I just want a new diff installed before the maggie gets here. I'll take it out and break it in the same day - most likely not the "correct" way this time. I don't care if there is a little whine in the end - but the carbon packs freezing up and the mini-spool style results - although likely great for straight line acceleration - are a nightmare the rest of the time.

By the way (threadjack on) - what exhaust are you running currently? Did you ever get to try a 2.5" B&B resonator? (threadjack off - we need threadjack emoticons!)

02-13-05, 03:40 PM
No, never tried the 2.5" B&B resonator. Wonder if I could still hear my wife four blocks away running through the gears with that version? :hmm: :lildevil:

My V had about 50 miles of city driving on it (trip to window tinter, etc.) before the seven hour romp. Those first miles spread over a few days gave the rear some good heat cycles. That along with changing the black disgusting fluid early at ~500 miles and then every 2500 miles since has worked for me. Perhaps luck was involved and I got a "good" one? The fluid looked good the last change; might be able to stretch the intervals from now on.

02-13-05, 10:36 PM
Mine now has Redline 75w90 gear oil in rear differential (no need for limited slip additive) with this Redline product (per Redline Website and an email to the company).
V now has 2000 miles, no whine.
Side note: My Corsa exhaust system produces a "whine" type noise in 3rd or 4th at 42 MPH until the vehicle is at operating temp.