Chevy & GMC Vans

I have a 2001 AWD van that started our as a rental van and hasn't had any mods. It runs great. The door RPO code shows GU6 for the rear axle. There are no other RPO codes beginning with 'G'. The owners manual says to use 80W-90 Axle Lube in the rear (standard?) differential, but the Factory Manual says 75W-90 SYNTHETIC. The Factory Manual is current to 2/16/01, but the owners manual was printed in 2000. Both differentials had full fluid changes at 32K, but I seen no record of a subsequent full change in any of my service records. I'm at 110K miles. I'm guessing I go with the 75W-90 with no friction modifier, and it wouldn't hurt to change fluid in both diffs? (80W-90 in the front)

Thanks

As you say the only G on the RPO sticker is for the gear ratio, you basically cant go wrong with rear end lube. No G80 means no limited slip so no special additives required. I use the same stuff for both diffs. One less bottle laying about

Thanks. I also found this Amsoil site that lists the fluid upgrades that have happened over time for this van, and lot of other specs.

http://www.amsoil.com/MyGarage/VehicleL ... RO%20VAN+W