gm recommends adding additive to the rear end when replacing all of the differential fluid.

can someone explain why additive is needed, or is it just a suggestion?

thank you

 

so does dodge...the rear diff is always under a GREAT deal of stress..im not even certain of what the additive is, i think that it is just a seal/gasket refresher of sorts.

 

Whatever it is, I'd add it. Its there for a reason.

 

Thd additive is to make the limited slip clutches in the differential from sticking together when turning corners. It essentially makes the lube slicker. If you didn't have it, you would here a clacking noise when you go around corners. [8D]

 

Correct, it is a friction modifier.

 

Both of these guys are right on the money. I've had some limited slip differentials in the past that still made noise after changing the fluid and adding the recommended additive but they quited down after I put in a second bottle of additive. If you have a noisey limited slip unit sometimes just driving the vehicle in tight circles in both directions in a parking lot helps. There are several styles of limited slip units on the market today and lubricant requirements can vary so always check your manual.