I have an 01 silverado with the auto 4wd. The rear end is a 3.73 with the optional locking differential. The rear end has the synthetic rear axle fluid.

When I changed the rear end fluid, I used the dealer GM synthetic rear axle fluid (which the jug indicates is grape scented!).

The question, which the dealer could not give me a definate answer, is should I add the limited slip axle lubricant additive? THe dealer indicated I probably should as it would not do any harm. He read the bottle which indicates to add this once you have filled the "axle with the appropriate axle lubricant."

So far there have been no chattering or other unusual noises.

Does any know for sure?

No additive needed here in the G80 locking diff.