Transmission tie up?

What your describing is shift overlap and it's very detrimental to a trans. Run it like that much and you'll be yanking the trans out for a rebuild. As 67Dart273 asked, did you follow the instructions when installing it? Most manual VB's require changing the front band apply lever to a specific lever. And if the rear servo still has the inner spring in it that could very well be the problem. It causes the rear band to release to slow