It should be listed on a sticker located in your glovebox in the form of an "RPO code" which I will leave it up to the masters here to tell you which code you are looking for.
Chances are if you have the towing package you have the 4.10’s nut check your RPO codes in the glove box, then check my first post here for the RPO code.not sure ill check on the info in the glove box but mines a 2wd with towing package and it has a locking rear diff if one spins faster locks the rear end and then open back up
I have the GT4 sticker in my 05 Suburban but I was told by the dealer it designates 3.73 not not 4.10 ???? :neutral:Rpo rear axle codes
There are a lot more but my eyes are getting tired.
GU2 would be the 3.73 rear axel code.
GT4 would be the 4.10 rear axel code.