th400 wont upshift full throttle

[whamo]

I bought a Switch Pitch TH400 freshly rebuilt. I cant seem to get the transmission to upshift at full throttle. I have to let off of the throttle to get it to upshift. I will hit the rev limiter at 6300 rpm and it still wont upshift, I have swapped out the governor, all that did was lower my partial throttle shift points. Im about to try a stock valve body. Do you have any ideas why I would have this problem? I have checked the modulator valve to be certain that it travels freely. And the kick down solenoid seems to be working properly.

[Hutch]

Usually that problem is governor related. If your switch pitch is really old,those transmissions used a governor with a different type of governor gear. The early gears had a tit sticking out of the end of the gear to locate the governor in its bore, the newer governors have none but there is a steel dowel that was installed into the trans case and the governor gear has a hole that goes over the dowel for location side to side. You may have a late governor in an early case . Other problems could be a plugged governor filter located in the governor feed tube at the case or in the valve body. The last would be a badly worn governor bore or trash preventing the governor spool valve from functioning properly.

Let me know what you see, Hutch