xts

What should I use in my alison 5 speed?

rrrr

Dextron III. I've started on my first change. Waiting to put a few more miles on it before I do another change to try and get rid of as much oil as possible.

After the first change I notice smoother shifting both up and down. The second change should make it even better.

I assume you are asking about the M939 series trucks and the automatic transmission. Do a search there is more information out there. You can also download the technical manuals on this site to aid in your understanding of the truck.

Have fun !