What is the man trans oil and capacity of an '88 mighty max?!

[JBird]

I need to know the best oil to use in my '88 mighty max manual trans and how much?

[SubGothius]

Owner's manual says hypoid gear oil of spec "GL-4 or better", 2.4 quarts (2.3 liters) -- basically, once it starts running back out of the fill hole on the side, it's full.

That said, I'm not sure they anticipated the later GL-5 spec would pose issues with syncro operation (too slippery) and "yellow metal" components (potentially corrosive to brass/bronze/copper), nor if those issues even pertain to our trans in particular. I'd just stick with GL-4 in the trans to be safe, tho' your differential(s) should be fine with GL-5.

Redline MTL is a great synthetic GL-4 gear oil, maybe consider their MT-85 or MT-90 if you're in a region with really scorching summers -- e.g., I'd prolly go with MT-90 here in Tucson where summer temps can get up to 120°F or so.