It was me!!!!! But I am probably the exception!!!
It was me who posted that the AMSOIL 2000 75-90 made my rear diff grind badly!!! And in my case, IT DID... When I changed my rear diff fluid for the 3rd time (Previous 2 times were by dealer, with MOPAR stuff) Within about 10 miles, I felt a slight grind on corners. It was most pronounced when pulling my gooseneck trailer. I didn't even consider it being the AMSOIL. It is GREAT stuff!! I thought my gooseneck ball was dry and grinding on the hitch. Greased that up, same grind. Around town it was OK, maybe little chirp here and there. Pulling, it was BAD. ONLY on corners usually! Sooooooooo before I took it to the dealer for repairs, I thought I would switch out the rear diff fluid just to see. I went to NAPA and got some VALVOLINE 75-90 100% synthetic lube. Put that in, Instantly, NO grinding whatsoever. Still pulling the same load, same driving habits, etc... Absolutely NO grinding. My rear diff was rebuilt at 2200 miles so she has not been real perfect since new. I think my truck is the ONLY one on here to have had the problems w/ AMSOIL... SO please don't stop using AMSOIL because of my dumb little rear diff, it's probably the first one in the world to react that way to it, however I did have 3 reply's of people who had the same experience as me!