Sounds like you may have done something incorrectly when the valve body was modified with the TF2 kit. I would suggest disassembling it carefully and go over the TF2 instructions very closely again. The TF2 instructions are a bit cryptic and hard to follow but the diagrams are pretty good. Otherwise a good shop manual would show the valve orientations. Pay particular attention to the 11/32" and 3/8" check balls as show in the attached diagram. If you get them mixed up, the symptom is no third gear.