[Alan Roehrich]

Yes, Hipster has a special gasket, or at least the last 2-3 I freshened did. You need them. Do yourself a favor and order 2-3 spare sets, they should be priced low enough you can do that.

Reverse requires the high gear clutches and the low/reverse clutches. Low gear requires the low/reverse clutches and the forward clutches. Mark Y is correct, it sounds as though it may have the low/reverse piston hanging or being applied all the time. What does it do in neutral and park?

There are three seals on the low/reverse piston. Your builder should have used the inner and outer, but discarded the "middle" seal. If he installed that "middle" seal, it may cause a problem.