If you are refering to the 6400 in photo,s it more than likely is the SM420 4 speed with granny low. They are easy to rebuild. Get a good manual & follow directions. The bearings , gaskets & seals are readily available but if you need any hard parts you will probably have to find used ones or get another one for parts. The T-5 you see mentioned is a 5 speed used in s10 pickups & other vehicles. A lot of us are putting them in the light duty trucks to get the o-drive feature. It would not stand up in a heavy duty truck.
