how vital is GM Additive for rear end
 

im changing bearings tomorrow and will have to open the rear cover to get out the clips. so far i bought a new gasket and 2 qts of mobil 75-90, however can i get away with not putting in the gm additive or will it cost me in the long run?

Additive should be used with a limited slip rear (not needed on an open rear):
Torsen General Frequently Asked Questions page

"Torsen for GM vehicles:

Is it true that the Torsen unit in the production Camaro needs the GM modifier added?
GM issued a technical bulletin adding modifier to the rear axle oil. This was done to quiet what we call a "Rusty Screw" noise that we heard in a very small percentage of vehicles. This does not happen in all cases, however to address owner's concerns we asked that the modifier be used in all instances to insure that the driver would not get this noise. When replacing the fluid it is at the owner's discretion whether or not to add the modifier. Elimination of the modifier does not affect durability of the differential."

well that sums that up! according to the window sticker Ive got a limited slip differential, and when i slam on the gas both wheels spin.

thanx

I've also read that the additive helps with the clutch friction to reduce slippage.

well, that went horrible, i spent hours trying to get the c clip off the axle with no prevail. so it was pretty much a gear oil change. at first it was clear and green coming out, then dark brown, car runs peppier now.


i think i may have some brake drag though. causes?

With the Torsen diff the addition of the stuff is optional but it does not hurt to add it to any diff limited slip or not. The friction modifier or posi additive does not have to be the stuff from GM but it should meet the same requirements that the GM stuff does.

Massey

cool, any idea on how to get that clip out to release the axle?

There is a bolt/pin that holds the middle gears in place, kinda like the pin that holds the spyder shaft in a normal diff.

Massey

yeah i did take out that block with the pin, but when i would pull/push the axle the clip wouldnt come out, magnet didnt do it, even tried hitting it out and no luck, did i miss something?

Did you remove the wheels and brakes so you could push the axles into the diff?

Massey