Chassis Tuning

Also you say you have a TF-2 shift kit.
If you don't have the Kick down adj just right, AND your manually shift it through the gears, you can burn up the 2nt gear band.(Or rev. band.)
When i went to a RMVB all of them problem when a way. Because there is no timing between rev band and 2nt band. Also make for a vary strong 1-2 shift. Mine is a 727, don't know if it completely apply to a 904 let alone a 904 Lock up TQ unit.
Just some food for thought......................................
Yah, hindsight being 20-20 this tranny was probably weak before I put the shift kit in and was shifted manually for quite a while prior to adding the shift kit. It did have a Lokar kickdown on it the whole time, regardless a manual valve body is the preferred direction for this application.