TH350 questions

Ok I have been having an ongoing problem here.
I have had an 80 firebird that I rebuilt and droppped in a 350 with some speed goodies, and backed it with a TH350 with a healthy shift kit. Now I dont know the specifics here because a friend of mine who is tranny savy built it. But about a year into driving the car the tranny wouldnt shift out of first. So we tracked it down to the govener(spelling sucks i know). So after replacing the part things were good again. This has happened about 3 diffrent times in the 6 years the car has been alive. Now the same symptoms are back, but the car will not even shift with me manually shifting. I have yanked the govenor and cleaned it out. And replaced the fluid and filter. I HAVE NOT done a complete trans flush. But it remains stuck in first, or sometimes starts out in second and just hangs there, so i am forced to limp home starting out in second.

So do you guys have any ideas?
I have a stand by TH350, but it is bone stock and i am afraid this motor may tear it up. And i really dont want to yank the 350 that is currently in the car if the fix is something simple, and my lack of knowledge is holding me back.

thanks guys

Yes it does have a Vac. Mod. But i have replaced that in my quest for a fix. And yes the fluid levels are fine. And you can feel every slot for the gears.

I am thinking it is time to make this a manual valve body, and just be done with it. Or build a 700R4. But i have a good chunk of change in this thing already.

Any other ideas

Sounds like you've got debris in your valve body. Probably around the 1st to 2nd detent plunger. It's not hanging up between shifts (feels and sounds like neutral), it's hanging up while still in gear, (not releasing). You stated that you've had the transmission for 6 years and you haven't done a flush yet.

Many years ago, we got away with a trans flush every 50,000 miles. Not so today. We should be flushing every year, or sooner if you drive it hard. If you haven't done a flush in 6 years, that's not the problem...It's the cause of the problem.

Also, you might want to look into the front pump (in the bell housing). The vanes might be worn and not creating enough pressure to operate the valves in the valve body.

make sure the passing gear cable is not stuck wide open. **)

I too would check the kickdown cable. Had the same problem w/mine. Turned out there was a small dent in the trans pan exactly where the cable goes into the side of the trans. It was holding it in every time I floored it. Good luck...