GM Limited Slip Differential Additive

Spooling

Member
Joined
May 24, 2001
I am planning to do a rear end "gear oil change".

Previously, I used to get everything from GM - namely the rear gear lube + one bottle of "Limited Slip" additive.

Is this additive available from the local Auto Parts Store - in an "aftermarket" brand name?

If I decide to get other-than-GM Lube - I am thinking maybe some "lighter-in-color" Valvoline. I wish to ask the rated viscosity - should it be 80w90?

Many Thanks !!!
 
Pretty sure GM still has it, they still build posi cars, Lakewood used to have it also.
 
A lot of gear oil's already have an additive in it. Plus you only need the additive if you're getting clutch chatter
 
When I did mine (on both the GN and my GMC), I went to my GMC dealer's parts counter and when I asked for it and gave him the part #, he looked at me like I was a moron and said he had no clue what I was talking about. I went to O'Reilly and got some from them - it wasn't GM brand, but I figured it was as good as any. I put a half-dose in the GN and had a little chatter, so I put the rest in after the test drive.
 
Personally I have ran Red Line 75-90 synthetic in my rear end (that use to chatter) for about 19 years and 90 thousand miles with alot of 1/4 passes and ALOT of street driving and have NEVER had one bit of trouble with the rear end. I did have it out about 5-6 years ago and did some upgrades to it and installed new bearings and seals and a new GM posi clutch pack. I know there is alot of pros and cons about synthetic oil being to slippery but it has worked for me for many, many miles. Actually when I had it out the bearings and gears still looked new but I already had all new bearings so I installed them. I have never heard one peep out of my rear end running Red Line and you don't need ANY additive.
 
Synthetics are steered from with clutch type rearends. Eaton for instance recommends NOT using it.

I used to run a bottle of additive and now I run valvoline dino 75w 90 and 1/2 a bottle of lucas with NO additive. Todays oils as mentioned have the additive in it.

If you still have the factory rear end cover get a drain plug kit and slap it in the cover when in therenso you dont have to pull it to drain.
 
If you still have the factory rear end cover get a drain plug kit and slap it in the cover when in therenso you dont have to pull it to drain.

Whoa man - excellent consept. Wish you would have said something a day earlier. Maybe next time.
 
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