If it has posi-traction you need just the GM additive, However if you have one of those locking rears, I have one in my 05 silverado, all you need is reg or better yet synthetic 75-90 rear end lube.
But if you do towing like a boat or something , use the heavyer lube 90-140
If you have the owners manual for your truck it might give you a number to go off.
Walmarts rear end lube is a good deal cheaper than any auto parts store and its the same stuff.
Corvette Store
99 Suburban rearend????
