My TH350 rebuild

[rs72z]

Are you talking about the drum that goes on top of the foward drum? If so that is the direct drum, it has the intermidate sprag on top of it. The direct drum has two seals on the piston and one inside the drum. Sometimes this piston can be tough to get in because of the inner seal in the drum. When it's down all the way it should make a clunk.
Aso make sure you put the element on the sprag back on the right way, if it's backward no second gear. That's also a light duty sprag if you are going to be working it hard or playing offroad alot it would be a good idea to replace it with a heavy duty element.

Was your foward clutches fried?