Gear oil/rear end ?'s

[Dennis Mouser]

2001 job 2 trac with 90K, 4.10 NON LS rearend, today at walmart I had the choice of 80w90 or 75w90 synthetic blend, I chose the second



spec would have been 80w90 but there wasn't a syththetic blend on the shelf in that weight, what is the difference (is 75w90 a GM spec?), it took the whole quart!, that thing was dry..sucks cause I have a leak and need to get it fixed.



I know it's not gonna save the rearend but just wanted to put sytnthetic or synthetic blend back in, I don't think I had to worry that much about draining since it was empty, there was alot of graphite like buildup on the plug when I pulled it off... I'm almost scared to pull it off and look from the back side...the rearend doesn't growl, just a hissssshhhh sound once above 30 mph, I think that is typical, I sure hope it'll last another 50K



I'm starting to pay off my CC bills now in prep of rearend work, exhaust and perf pads/rotors (grand easy!)

 

[Rodger Tellefson]

First mistake was taking it to WalMart. I put the recommended Royal Purple in the differential on our '01 w/ LS and got 1 more mile per gallon. Don't know how much adding the Trick Flow differential cover made because it was added at the same time.

 

[Tom Schindler]

Don't know how much adding the Trick Flow differential cover made because it was added at the same time.

The diff cover won't improve economy or performance, but it does help strenghten the rear-end up because of the bolts that support the bearing caps.





Tom

 

[Johnny O]

The 75w-90 should be fine. For my '05, the manual specs 75w-90 for the rear on one page and 75w-140 on the next page. I put in Mobil 1 75w-140. Probably the 90 would get better mpg.

 

[Todd Z]

75w90 is the recommendation for the open diff, IF you have a limited slip you need the 75w140 with the friction modifier additive...

Todd Z