My owner's manual says to use 75W-90 gear lube in the tranny, t-case and front diff and to use SAE 90 in the rear diff.

Is 75W-90 too thin for the rear? My truck is a daily driver and I'll use it to flat tow my suzuki to the trail head.

Can I go with 75W-90 in the rear?

 

The FSM states GL5 80w-90 or 80w(below 0deg), or 90w(above 0deg) for both diffs. The exception being the ADD front diff, which can use GL5 75w-90.

See this page:http://personal.utulsa.edu/~nathan-b...21lubrican.pdf

I use GL5 75w-90 semi-synth in everything except the transmission (non-synth GL4 85w-90). My excuse being that it's partly synthetic so it's gotta do as good or better than the regular 80w-90 or 90w, right? Plus, it's what's available. Jerks want $20 a quart for the full-synth 80w-90. I change it pretty often too (yearly or more). It's all 90w at operating temps, so who cares. Just don't do no burn-outs till the gears warm up.

What brand?


Valvoline Durablend "Tough Driving Formula" GL-5 SAE 75w/90
A high performance partially synthetic gear oil formulated to provide enhanced performance and protection over a wide temperature range.
For use in all hypoid and other gear sets where an API GL-5 or US MIL-L-2105D performance is specified.

$4.39/quart.