Diff Fluid Change

SilveradoWV · July 15, 2002

I got a card in the mail today telling my my 3000 mile service is coming up, which i have already passed it and done it. Anyway it said to change the Rear Diff fluid after the first 500 miles of towing! I probably havent towed that much yet, but will be coming up on it soon! Should I change it, I think it comes with synthetic in it. Also I was wondering what came in it? Is it GM synthetic or is it another company's product. I know when I had my ZR2 someone on a board I was on had lab access and tested his diff fluid and it matched Havoline Gear Oil! What should I use and how many quarts will it take?? Some people say 2 and some people say 3 just incase, I dont wanna pay alot for a third quart of synthetic if its not needed. Thanks!

GreenRado · July 15, 2002

My rear diff. came to exactly 2 qts 75W-90 Mobil 1 synthetic - 1/2 ton 3.73, non-locker 4x4. I used a handy-dandy tip (I think from Tom) for checking the fill level - use the short leg of a hex wrench that has an inside length of 1", which is what my pumpkin calls for. I think GM can sell you their version - they may recommend an addative, or maybe that's for the locker - not sure, and it'll likely cost more.

Incidentally, when my rig had ~ 500 miles on it, thought I'd check the rear diff and couldn't find the level, so I just drained it and got all of 1-2 cups!!! No leaks either - I think they just didn't put much in it @ the factory! Didn't appear to do any damage at least in that short of a time.

01_silverado · July 16, 2002

I just finished reading my owners manual and I can not see where it says to change the diff fluid at 500m. Can someone help me find it?

Thanks Pat

SilveradoWV · July 16, 2002

Its not in the manual, or at least I couldnt find it either!!! It WAS on my postcard I get from GM to remind me of what needs to be done! Like time for an oil change and time for tire rotation and all that stuff! Well on this card it had my scheduled oil change at 3000 miles and lube. It also said that the diff fluid needed to be changed after towing break in, and in parenthasis it said that it was after 500 miles of towing!!! So I guess I better change mine soon!