Gear Oil / Fluids

digizure

New Member
Joined
Apr 9, 2026
Messages
3
Location
Maryland
Hello, I have a question. I’m getting my YJ back on the road after sitting for ten years, and I’m having a hard time finding the fluids I need. AutoZone and Advance Auto have switched mostly to synthetic. I was able to find 10W-30 motor oil (Castrol GTX), but I can’t find Valvoline 75W-140 (conventional) for my Dana 30 and 8.8 with lockers, or manual transmission fluid that isn’t synthetic.

What do you guys recommend?
 
75W-140 is pretty much entirely synthetic. If you want conventional go with 85W-140. I use Torco 85W-140 in everything, even my brand new truck.

For manual transmission fluid I really like Driven conventional 80W-90 GL4. It’s perfectly fine as a substitute for the factory recommended 75W-90 GL4. The driven stuff shifts better than anything I’ve used. 75W-90 is usually synthetic or synthetic blend. I think the conventional oils stick to the metals better which is probably what improves the shift feel I notice.