Gearbox Oil

[tassuperkart]

80-90w gear oil is the same viscosity as straight 40w motor oil. (different way of designating gear and engine oils)
its formulated to compliment hypoid diffs and synchros.

Many truck gearboxes without synchro use straight engine oil in the boxes.

I actually use auto trans fluid in my VW transaxles. This is ONLY for reducing friction losses in an already very inefficient transmission. When you only have around 45 Hp at the wheels, ANYTHING helps!

Auto trans oil is a straight 15w oil and does not absorb shock or impact loading very well nor does it lubricate hypoid type diffs or spur cut gears correctly.
Synchro engagement tends to be notchy and the transmission runs fairly hot.

We dont have a hypoid type of diff in the poohser so you could run atf but the boxes tend to run fairly noisy and synchros might suffer in the long run.
Id also be fairly concerned about shifter forks as well.

Just use any 80-90w gear oil