I know this is an old thread, but maybe I can help. When you had no reverse, did you have fourth gear?
In this trans, reverse has first clutch on.
First gear is first and forward clutches.
Second gear is second and forward clutches.
Third gear is third and forward clutches.
Fourth gear is fourth and forward clutches.
Reverse is first and fourth clutches.
The clutch apply pressure cascades through the relay valves in this valve body. It's possible if you had no reverse, but had fourth gear the 1-2 relay valve was stuck in its stroked position. Reverse pressure goes underneath the 1-2 relay. However if that were the case, you would be shifting 2-3 and 3-4 in forward with no first gear when in drive.
If you didn't have fourth, and had no reverse, the 3-4 signal valves or the relay valve could be sticking in the de-stroked position.
It's also possible fourth clutch itself has a problem. It could be a burnt clutch, failed seals, or check balls in the clutch housing leaking. It could also be the sealrings on the forward hub of the center support.