Corvette Z06 Forum banner

Question about changing differential gear oil.

6K views 12 replies 9 participants last post by  touring2 
#1 ·
I had no problem changing the gear oil in my 99 SS. I just pulled the differential cover off, cleaned the pumpkin out, put on a new gasket and filled it up with Royal purple and a bottle of additive. My question is, how hard is it to change in the Z and what brand does everyone else use. Also, do I need to use the GM additive to keep the noise down like I did in the SS?
 
#2 ·
http://www.picturetrail.com/gmblack3/647207

Here is the info I got from Redline and amsoil about the GM additive:

The GM part # is 1052358. You should add this before putting the new fluid in the diff.
The local stealer here charges $9 for it. GMpartdirect.com shows a list of $5 but you have to buy 12 of them.

Amsoil and Redline claim that there fluids already have an additive in them. Amsoil says it both ways on there website:

AMSOIL gear oils are formulated with friction modifiers for limited slip differential applications. There is no need to add limited slip or additional additives.

AMSOIL Series 2000 Synthetic Gear Lube provides limited slip performance. Although generally not necessary, original equipment manufacturers' limited slip additives may be used in conjunction with AMSOIL Series 2000 Synthetic Gear Lube.

Redline says:

LIMITED-SLIP COMPATIBILITY Red Line Gear Oils, with the exception of the 75W90NS, already contain friction modifier required for operation in limited-slip differentials. Additional additive is not required.

I have emailed Redline and asked them if it would not hurt to add the GM additive to Redline.

Here is the reply from redline

The 75W90 would be suitable for the limited slip in your Z06 it contains 5% friction modifier, typically what is needed to reduce the chatter from the limited slip when making a slow tight turn. Adding more friction modifier if it isn't needed reduces the lock up of the limited slip and reduces it's effectiveness, so I wouldn't add it unless it is needed due to chatter and then only just what is needed. The friction modifier isn't a lubricant but just an additive to make the fluid slipperier for chatter control. The 75W90 should be suitable right out of the bottle without the need for the additive. Thank you for your interest in Red Line Oil.

It states in the GM manual that no WOT for 300 miles after the diff fluid is changed.

I used Amsoil series 2000 75-90w in mine with the GM additive and have had no problems
 
#4 ·
Var said:
That sounds like BS. can anyone verify? there's no way i'm driving the vette without WOT.
How did you find this thread? It is about three years old! :lol:

I actually looked the service manual for this issue this morning. This is what it says:

"Do not operate the vehicle at wide open throttle for a minimum of 300 miles after refilling the differential with lubricant and friction modifier. Scoring of the ring and pinion gears may result, leading to differential noise."

Since this thread is so old, I'd like to point out that the AMSOIL Series 2000 gear lube was replaced with this:
AMSOIL Severe Gear Extreme Pressure Synthetic 75w90
I use this in my car on the track and have not experienced diff chatter so do not add the friction modifier to my diff. :cheers:
 
#6 ·
Var said:
That sounds like BS. can anyone verify? there's no way i'm driving the vette without WOT.
Here is the procedure:


Draining Procedure
1. Raise and support the vehicle. Refer to Vehicle Lifting.
2. Clean any dirt from around the differential drain plug.
3. Remove the drain plug and washer from the differential.
4. Drain the fluid.

Filling Procedure Notice: Refer to Fastener Notice in Service Precautions.

Important: Do not operate the vehicle at wide open throttle for a minimum of 480 km (300 miles) after refilling the differential with lubricant and friction modifier. Scoring of the ring and pinion gears may result, leading to differential noise.

1. Install the drain plug and washer to the differential.
A Tighten the differential drain plug to 35 Nm (26 ft Ibs.).
2. Clean any dirt from around the differential fill plug.
3. Remove the fill plug, lubricant tag, and washer from the differential.
4. Fill the differential with fluid:
A Fill with synthetic axle lubricant GM P/N 1237826 (Canadian P/N 10953455).
A Add approximately 118 ml (4.0 oz) limited-slip differential lubricant additive GM P/N 1052358 (Canadian P/N 992694).
5. Check the fluid level to ensure it is even with the bottom of the fill plug hole to no lower than 6 mm (0.25 inch) below the opening.
6. Install the fill plug, lubricant tag, and washer to the differential. A Tighten the differential fill plug to 35 Nm (26 ft. Ibs.).
7. Lower the vehicle
 
#7 ·
just don't overfill-mine spit out fluid after i drove it hard , about a "quarter" in size spot on garage floor..guys i talked to recommned to let it drain out and then some, for proper fill
 
#8 ·
Var said:
So the 300 mile thing is BS right? I might give it one heat cycle at most.. I was planning to refill with the Amsoil.
No, that is actually what it says. Now, if you don't follow that, who knows how much scoring of the ring and pinion actually occurs? I certainly don't know.

Thanks for your support of AMSOIL. I'm dropping you a PM with info on the AMSOIL Preferred Customer Program. :cheers:
 
#10 ·
Var said:
I never doubted that's what it actually says. It also says to put dex-cool and Mobile One in my car. I will never use either of these products again. I'm asking is it BS, as in...is it true? It makes no sense. I got your pm and responded. Thanks.
It does seem to be a bit of overkill, doesn't it? I know most SCCA T1 guys just replace their fluid, do a few figure eights to work in the new fluid, then go beat the heck out of the car, myself included. Also doesn't really make sense to me that none of the old fluid would be "worked in" already providing protection. Its not like it was dry before you added the new fluid.

But, on the other hand, there are a lot of drivetrain noise threads on the various forums these days and they don't seem to have a common theme. Wonder if this could be a contributor. From my casual review of the threads, the throw out bearing seems to be a common culprit.
 
#12 · (Edited)
The 300 mile precaution when changing the Diff (and Tranny) fluid is correct and for good reason.

When the car is brand new the engine breaks in at around 500miles minimum, however the Tranny and especially the Diff require almost a 1,000 mile break in. It takes that long to burnish in the gear faces and harden them somewhat.

New fluid partially removes some of the burnish layer....similar to deglazing a saute pan with wine. With new fluid the gear faces need to be reburnished, which takes place in 300 miles.

If you run the car hard initially before the 1,000 mile break in and subsequently before an additional 300 miles after a fluid change; you will scoure the soft gear faces. This may lead to more "chatter" and premature failure.

Synthetics such as RedLine and AMSOIL may offer additional protection and are more resistant to heat break down, and may function as some friction modifiers do and be safe on the street without the additional Additive.

However, I still recommend using the 4 oz Additive, especially on tracked cars. AMSOIL's Slip Lock Additive is up to Spec with GM's and is cheaper.

I use & recommend:
AMSOIL's Synthetic Severe Gear 75W90 Extreme Pressure Lube, with
4 oz. of Slip Lock Additive
in the Diff.
 
#13 ·
Re: 10 year old post, Question about changing differential gear oil.

The 300 mile precaution when changing the Diff (and Tranny) fluid is correct and for good reason.

When the car is brand new the engine breaks in at around 500miles minimum, however the Tranny and especially the Diff require almost a 1,000 mile break in. It takes that long to burnish in the gear faces and harden them somewhat."Quote]

Had the diff replaced last year with a hellacious howl. Believe it was gears and not bearings, but didnt' tear down. this was after 10 years of a lot of street driving, but maybe 9, - 10,000 track miles, as a SWAG given the many track days I run. But , I dont' think I put 300 miles on the lube before track days. I mean, who reads the manual, anyway(Since I left subs, Brad!) And didn't change it as often as I probably should have out of ignorance. Since R&R of diff, I am changing every track day! may be overkill, but since I'm taking the Carbotechs off, why not do the lube at the same time? Still can't guarantee I'd put 300 miles on it before next track day.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top