Parts store 75w-90 for G80 rear end

[Rkaroll953]

Anyone find anything from the parts store that is synthetic without friction modifiers for our rear ends? looking to do that this weekend as i have some free time but my searches on here only result in people arguing about changing the fluid too early or recommending amsoil witch i dont know anyone who is a dealer. trying not to spend the 30$ a quart at the dealer if i dont have too.

 

if you have found a brand that you have had luck with that i could just go and pick up ( napa, autozone, ETC) please share!

[newdude]

The rear diff uses 75w85 on your truck, not 75w90. 19300457, $22.25 per quart from your dealer.

[LongrangeLauber]

I've used 75w90 with no ill effect. You can order online through amsoil but there are a few dealers on here. Just put some in my truck, good quality stuff. I really noticed a difference with their trans fluid over the valvoline crap I removed from it

[Krusty]

How about Mobil 1 - that's what I ran front and rear in my 2007.5 2500 Duramax with the G80 locker.............

 

https://mobiloil.com/en/gear-lubricants/mobil-1-synthetic-gear-lube-ls

 

[Cowpie]

Yeah, 75w90 will work fine. The 75w85 may be an OEM recommendation, but that is only a recommendation based on fuel economy game. I use 75w90 in everything from my pickup, my Cadillac CTS, my semi trucks, even my garden tiller gear box. One gear lube for everything and sure not some stupid $22+ a quart nonsense.

[SavageSierra]

I've never had an issue running 75w-90 Mobil 1 LS and Royal Purple 75w-90 in several G80 rear ends. Don't worry about the 75w-85 recommendation, i was in the same boat as you and i called my GMC dealer and the technicians said they use 75w-90 in the G80 and it works just fine.

[Rkaroll953]

yea im not gonna use the 75-85 the truck has big heavy tires M/T tires and sees a trailer a couple times a month id rather use the 90 weight.