The shift at 15 MPH won't happen until I let off the throttle. After the shift, if I use more than 30% throttle it drops or of gear and will do that between 15 and 25 MPH. After that everything seems fine.

Most of the threads on this topic I have already looked at. Most said it was the gov solenoid. I replace the gov solenoid and the pressure transducer and still have the slip. I am going to check the front band as soon as its warm enough to roll under neath it.

Any other thoughts on what to try or am I looking at a rebuild?

 

It has been 7 years since it was rebuilt.
Thinking about it more, maybe it was completely missing 2nd gear and that was the issue.