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#516831 - 08/02/05 10:40 AM Rear diff oil in 2002 Camaro Z28 question.
Chris B. Offline


Registered: 03/16/03
Posts: 2898
Loc: Colorado
I changed the diff oil at 20,000 miles using Mobil 1 75w90 synthetic. The owners manuel reccomends synthetic oil. The car now has 31,000 miles and seems fine. I just read that you should add limited slip oil additive also and is reccomended by GM. I did not know this and never put it in the diff 11,000 miles ago. Did this do any harm? The rear end is not noisy and seems fine. Thank you!

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#516832 - 08/02/05 04:42 PM Re: Rear diff oil in 2002 Camaro Z28 question.
Mike_dup1 Offline


Registered: 11/17/02
Posts: 3011
Loc: USA-Michigan
NO the additve is only a friction modifier to correct what the lube cannot do. Most all synthetic lubes don't need it. You will know if you need it by the noise it makes. Referr to the .


Here is an excerpt from a GM TSB

quote:
Shudder of Bind On Low Speed Turns - keywords
axle differential groan growl moan noise rear
slow vibration #PIP3152E - (Apr 26, 2005)
Shudder or Bind On Low Speed Turns
2004-2005 Cadillac SRX, CTS, CTS-V
2005 Cadillac STS
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.
Condition/Concern:

Customer may comment of a shudder or bind from the rear of vehicle on low speed turns such as
parking lot maneuvers on vehicles equipped with G80 limited slip rear axle. This condition may be more
noticeable with the vehicle at operating temperatures.
Recommendation/Instructions:
Flush the rear axle assembly and refill the fluid with P/N 12378261 (Canadian P/N 10953455) and also
add additive P/N 1052358 (Canadian P/N 992694). Fill level should be at the bottom of the fill plug
threads in the housing. The vehicle should be driven for a minimum of 20 miles before re-evaluating the
concern.
Please use Labor Op F3272 Plug, Differential Carrier Drain - Replace when performing this PI.


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#516833 - 08/02/05 07:01 PM Re: Rear diff oil in 2002 Camaro Z28 question.
aualtima3.5 Offline


Registered: 04/13/05
Posts: 113
Loc: Tn
I had a 94 Formula Firebird that would moan w/o the GM Limited Slip Additive. Then again, they changed the diff from torsen to auburn limited slips when around 97 or whenever the LS1 came out.

If it isn't making noise or binding up at low speeds, I wouldn't worry about it.

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#516834 - 08/03/05 09:52 AM Re: Rear diff oil in 2002 Camaro Z28 question.
Chris B. Offline


Registered: 03/16/03
Posts: 2898
Loc: Colorado
It is making a little noise almost like a ratteling moise but it did this when new and the dealer said it was a normal noise for posi traction diffs.

What exactly does binding feel like?

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#516835 - 08/02/05 11:31 PM Re: Rear diff oil in 2002 Camaro Z28 question.
Ryan00TJ Offline


Registered: 07/08/02
Posts: 742
Loc: Lake Anna, VA
I've always added the FM along w the M1 75W-90 in my 02 LS1. The rear is dead quiet.

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#516836 - 08/03/05 04:08 AM Re: Rear diff oil in 2002 Camaro Z28 question.
Mike_dup1 Offline


Registered: 11/17/02
Posts: 3011
Loc: USA-Michigan
It fells like the car is jerking at slow speeds but you will only notice this in tight turns, like in a parking lot or around a 90 slowly. What is happening is that the clutchs are sticking and both wheels want to turn when it really not suposed to. Normal rattling it not what it is, I could ppund on the wheels on my car and hear the axle rattle and thats normal, nothing loose. You may hear a loud clunking noise also from the tires gripping the pavement, won't hear it on soft ground. LSD axles have always been noisey, trust me I have had many of them going back to the 1960's. That was always a drwaback to them, you had to life with the noise. Customers drive service depts crazy over the noise but you have to live with it. You won't noise it on a truck as much because the interior is not sitting on top of the axle where the noise can be easily heard.

I dont' know where the Auburn comes from but the stock GM G80 in the F-body is a Thorsen. Auburn was a upfitter option (SLP) in the Firehawk or Camaro SS. Those are models that GM did not build, but farmed out to SLP and the customer could order peformance axles, suspension for a lot of extra cash + a long wait for the car. I had a 2002 Trans Am WS6 and it had the Thorsen.

btw-It won't harm a thing if you use the additive.

Here look at the window sticker and see for yourself about the Thorsen..
 -

[ August 03, 2005, 07:25 PM: Message edited by: Mike ]

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#516837 - 08/03/05 12:00 PM Re: Rear diff oil in 2002 Camaro Z28 question.
Chris B. Offline


Registered: 03/16/03
Posts: 2898
Loc: Colorado
I'll probibly add it soon. If it needed it(limited slip additive) and I have been driving around with out it for the last 11,000 miles could I have done any damage or caused a lot of wear to the diff?

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#516838 - 08/03/05 05:06 PM Re: Rear diff oil in 2002 Camaro Z28 question.
Mike_dup1 Offline


Registered: 11/17/02
Posts: 3011
Loc: USA-Michigan
No, not likely unless you have been abusing it a lot.

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#516839 - 08/03/05 10:28 PM Re: Rear diff oil in 2002 Camaro Z28 question.
Chris B. Offline


Registered: 03/16/03
Posts: 2898
Loc: Colorado
My wife drives it most and she rarely takes it over 4,500 RPM. I have done exactly 2 cookies once to show a dumb friend of mine that Z28's have a little more power the Honda Civics!

I'd say 95% of the driving the car sees is gentel/normal driving.

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#516840 - 08/04/05 02:07 AM Re: Rear diff oil in 2002 Camaro Z28 question.
Mike_dup1 Offline


Registered: 11/17/02
Posts: 3011
Loc: USA-Michigan
Well you have nothing to be concerned about. I never put any in my WS6, none at all and ran Amsoil 75W-90 for the 20,000 miles I had the car. The CTs has G80 and I have Amsoil Severe Gear in it w/o an additive. Don't hear any noise but car has 4,700 miles and 4,000 on the gear lube.

This best describes the case for the additive.

quote:
Customer may comment of a shudder or bind from the rear of vehicle on low speed turns such as
parking lot maneuvers on vehicles equipped with G80 limited slip rear axle. This condition may be more
noticeable with the vehicle at operating temperatures.


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#516841 - 08/04/05 05:25 PM Re: Rear diff oil in 2002 Camaro Z28 question.
TooSlick Offline


Registered: 08/02/02
Posts: 5785
Loc: Dixie
I'd try this stuff:

http://www.amsoil.com/storefront/ada.aspx

The Amsoil sliplock additive will smooth out this chattering and allow you to "tune" in the right amount of friction modification.

Tooslick

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#516842 - 08/05/05 09:55 AM Re: Rear diff oil in 2002 Camaro Z28 question.
Chris B. Offline


Registered: 03/16/03
Posts: 2898
Loc: Colorado
Thank you again guys!

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#516843 - 08/05/05 02:29 AM Re: Rear diff oil in 2002 Camaro Z28 question.
Triaged Offline


Registered: 08/04/05
Posts: 16
Loc: SoCal
The Torsen diff doesn't have clutch packs and so doesn't need a limited slip addative. The Torsen is a Torque Sensing (hence the name) differential. It works based on the friction of the gears against each other. While the synthetic oil will make the R&P last longer the reduced friction will reduce the bias ratio of the diff (make it easier to burn out one tire). If you don't have problems with traction don't worry about it but if you have traction problems you might want to stick with the dyno juice.

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#516844 - 08/05/05 02:45 AM Re: Rear diff oil in 2002 Camaro Z28 question.
Mike_dup1 Offline


Registered: 11/17/02
Posts: 3011
Loc: USA-Michigan
Note-I am told GM installs Synthetic at the factory, mfg is Texaco.

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