rkj427

chatter or binding condition on low speed turns AND friction material debris in the lube.....................

incorrect additives actually degrade (attack) bonding material of the friction material to the clutch plates.................

LowRyter

I used the correct fluid and GM specified additive according to the owner's manual.

LowRyter

to be clear, the owner's manual in my '08 specifically calls out for GM additive.

I understand that GM came out with a SB and changed the fill. I would assume that at that time, manuals were updated.

If I had the SB at the time, I likely would've saved some $$ and aggravation and forgone the additive. As it it now, the additive and new fill have worked fine. No more clicks in the rear end.

dmk0210

That must be it. The OMs must have been changed starting in '09 or '10 Does anyone know what Service Bulletin # that was?

My 2010 owner's manual makes no mention of an additive in either the Recommended Fluid section (7-10) or the Rear Axle section (6-55).

AORoads

^^ I recall it was the second change of fluid type/conditioner that was the final fix and if I recall correctly it did occur sometime in either early or late '08. That means additive already in the fluid, no separate additive needed or wanted. Mine being one of the first built in the model year (July, '07) it was subject to the redo and was done at the dealer sometime in early/mid '08.

C6_Racer_X

One major tip for the do-it-yourselfers here.

Always loosen and remove the fill plug first, before removing the drain plug. Partly, that helps it drain better, but the most important reason is how bad it sucks to break your wrench or round out the seized up fill plug after you've already pulled the drain plug and drained the lube out of the thing. Don't ask me how I know this.

PS. Using a vacuum device at the fill plug hole completely avoids any risk of that issue.

05 Wreck

Going to use my MityVac to vacuum most of the fluid, then remove drain plug for the rest.
(05 drain plug above rear spring) Hope this eliminates mess on the garage floor. GM LS fluid for fill.

windyC6

Heck...the more things (tools) you have to handle during any job like this seems like it would be more apt to cause problems. Just get a big drain pan and drain it all out the drain......

windyC6

So if i'm getting no chattering or binding then i'm probably good to go ??

dmk0210

Put it in competition mode then do a burn out. You should get two strips of rubber. That's the only way to know for sure.

rkj427

should be good to go......................

if you did add the "additive" previously, that was never stated anywhere that I saw...............
you may not have had it installed for a long enough duration, or utilized the clutch plate operation enough to cause any detrimental effect.............. or accumulated enough mileage for it to potentially impact the bonding agents on the friction material..........

too many unknowns or not enough information provided to say with 100% certainty

LowRyter

my '08 owner's manual (cut and paste)

What to Use
To add lubricant when the level is low, use
SAE 75W–90 Synthetic Axle Lubricant (GM Part
No. U.S. 89021677, in Canada 89021678) meeting
GM Specification 9986115. To completely refill after
draining, add Limited-Slip Axle Lubricant Additive
(GM Part No. U.S. 1052358, in Canada 992694). See
Recommended Fluids and Lubricants on page 6-11.
Then fill to the bottom of the filler plug hole with
the Synthetic Gear Lubricant

6-11

Rear Axle
(Limited-Slip
Differential)
SAE 75W-90 Synthetic Axle
Lubricant (GM Part No. U.S.
89021677, in Canada 89021678)
meeting GM Specification 9986115.
With a complete drain and refill, add
4.7 ounces (140 ml), or 6.8 ounces
(200 ml) for ZO6 Models, of
Limited-Slip Axle Lubricant Additive
(GM Part No. U.S. 1052358, in
Canada 992694) where required.
See Rear Axle on page 5-51.


it's my understanding that this was superseded by a service bulletin. However, the GM additive is still available and the service fill cured my rear end "clicks" approx 2 years ago.

dmk0210

Did you use that with the #88862624 Dextron LS 75W90 or the #89021677 75W90?

Not So Fast

I tried to find the service intervals or recommended mileage for changing out the Diff oil but no luck, probably missed it so what say you gurus about this.
My 2011 GS has 30,000 mi. and obviously about 6 years and as far as I know never been changed. Having no problemos BTW
Thanks
NSF

windyC6

Was just wondering cause I put the Purple stuff (additive already in it) in about 7 years ago and haven't had a problem since. Kinda hard to believe that the clutch packs would be so "sensitive" that they would have to use the exact lube that GM happens to sell. Kinda like Harley insisting that owners use "Only" Harley oil and i've been using what ever quality syn is cheapest in my Dyna now for 10 years and no issues. Has anyone in this forum ever had the clutch packs actually fail due to having the wrong lube in the unit ?? And if the clutch packs did fail, how did they know they were toast ?.....

Dano523

Jack up one side of the rear end until that tire just clears the ground, chock the front tires with the E brake off , then put a torque wrench on the spindle nut of the axle side with the tire slightly up in the air, turn the spindle nut clockwise and see what the break away torque value is when the wheel starts to turn independently of the other rear tire that is on the ground and stationary.
Note, spindle nut is torqued to 140ftlb, and is loctite in place, so it will be the axle turning via the nut, and should not be the nut turning on the axle shaft at the 100ft lbs that the clutch pack each side should allow that axle to turn indepently of the other tire side.

The correct break away torque value for the LSD clutch packs to allow each axle side to slip independently of the other side is 100ft lbs.

So that note, once you have checked one axle side, do the same for the other side, and check that side break away value as well.

C6 diff, and you have a clutch pack on each side, for each axle side.

mikeCsix

Good Info Dano, Thank you!

mikeCsix

My '12 GS has 24k and I've changed mine 3 times already. The first time had a lot of sparkle to it so you may want to consider changing it.

FYI, the differential gets pretty hot on the race track, hence the frequency.

dmk0210

I've looked too. I don't think GM has a recommendation.

Katech recommends changing it often on tight road courses. I'd imagine autocross or tight roads street driving would also exercise the diff quite a bit.

KayJay

Same issue as Not So Fast - what is the recommended interval for changing diff oil? Have a 2010 coupe with 34K miles and original diff fluid....thanks for any information.