2000 GMC Sierra 2500 4x4 diff oil help

91710zx10 · June 24, 2014

Ok, I've read and read but I'm still confused about gear oil as I would like to change my fluids. I live in Southern California so no worries about freezing temps. They also do not sell amsoil gear oils in my local parts stores cause several recommend 75/90 full syn. Yet some say it is safe to use both front and rear and others say no. ALSO, my truck is the in-between years of a full HD And just a 2500 3/4 ton so I suppose it's different. It is push button for 4 wheel so I also need to know which oil to use in the trans case please. Will I need and additive or not cause that's another confusing topic. Sorry gents for my lack of knowledge but I've only changed oil and trans in the truck and never gear oil. I do tow maybe 10 times a year a 19' toy hauler so I imagine I tow 7000 lbs fully loaded. And this truck is not my daily driver and I probably only put 5000 miles a year on it and it's at 135k now and the second owner which I bought with 120k miles years ago. Thanks for your patience with my long post.

Chris · June 24, 2014

The differentials use no additives.

8.1HD/ALLISON · June 24, 2014

75w90 is fine. No additives. Can't think of the transfer case oil off top of my head right now. Check owners manual, should have name to reference.

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sdeeter19555 · June 24, 2014

You should be able to find the owner's manual online somewhere...that would tell you the fluids you need.

Any good brand name gear oil will be fine...most failures are from not changing it at all. In my 2012 manual, they recommend 75w90 front and rear for the 2500HD, and 75w90 rear/80w90 front for the 1500.

If the transfercase is a push button then I want to remember reading it uses either ATF (electric shift transfercase) or AutoTrac Fluid (for the automatic 4wd transfercase)??