need trans help! completely lost on this one.

Usually when only reverse works and then it quits driving, it's either low on fluid or the lip seals are hardened up from age and don't like to seal anymore.
Especially if there is no metal in the pan.

IMPORTANT questions that will make all the difference.

Did it hesitate to move when it was not warmed up yet?
Did you ever have to rev it to get it to engage.
Is the fluid level low, just right, or over full.
If you chk the fluid before you start it it should look over full, and then when running the fluid level is normal? (This would prove if the pump is running or not)

I can answer again real soon if you answer these.