I use Castrol TranSynd which is an Allison approved TES 295 ATF. It is good for 150,000 miles or 4,000 hours or 48 months as compared to the TES 389 ATF at the Chevy dealer which is good for 50,000 miles or 2,000 hours or 24 months. My local Allison shop has the TranSynd which is what they use for all commercial vehicles. Cost for the ATF change at the Allison dealer costs less than the change at the Chevy dealers with the inferior ATF.Hey guys, so i recently bought my truck and am now looking into doing a service on the transmission. So, i did a bunch of research and now am worse off than if i did not look into it. So, what do you guys use for ATF fluid? do you guys take the pan off to clean it out? Use the OE Filter or a aftermarket? I am leaning towards Amsoil ATF or their Torque Drive ATF, anyone have any experiences?