Forum:
Hi, I am changing all lubes and fluids on my 1997 Sportrak. Can someone please tell me exactly what oil to put in the diffs?
Is it a limited slip diff?
The handbook states SAE 90, does this mean I can put EP 80w/90 
The vehicle will soon being going to an area of high temp (Sahara desert) will this affect anything?
Well Oiled
Yes, 80/90 will suffice in your diffs, gearbox, and transfer case. Most gear oil is multigrade to be slightly thinner to reduce friction, while still giving the same, or better protection.
While on the issue of lubrication, consider changing the grease in the wheel bearings, this is often neglected by most owners, and could become a serious problem in such dusty climates.
When you return from your trip, change them all again, it is suprising how much contamination gathers in such a short time.