My 84 Delta 88 only shifts at its highest predetermined points. 1-2 at about 17-18 miles per hour and 3-4 at about 41 miles per hour. Doesnt matter how you drive it. TV cable is good and is adjusted properly.

My brother and I had rebuilt this trans (first and only one we ever did) and we cleaned out the valve body and thought it was good.

What could be the problem? Could it be in the valve body?