TH350 problems

[ummduh]

Hey. New to the boards, actually here trying to find help for a internet-stupid freind of mine. Got a 85 K10, not that it matters, running 350/350/np205 setup in it. Having problems with the trans all of a sudden. Well, not so all of a sudden, the trans sat for a year or so before we got to it. The problem is with 3rd gear, as in we are having hit-and-miss engagement with it.
On decel it seems to be in 3rd, but as soon as you touch the gas, you can feel it drop right back into 2nd.
We've changed the governer, and it had 3rd for about 15 minutes after that. But when he let it sit over night, there was no 3rd gear again. We disco'd the kickdown cable, it's not hanging up or anything. Changed the governer to a known good unit.. Haven't touched the vacuum modulator, but it isn't leaking trans fluid or vacuum.

What else could there be? We don't really want to have to yank the trans again! (went through 3 700's before this, he doesn't get along too wel with auto trannys..lol)

Thanks,
Matt

[ummduh]

Wow, nobody knows anything about this?.. Err, well, thanks anyways. Good thing I'm not a GM guy, finding generic motors info is kinda difficult compared to "Brand X".

[Truckin Fool]

Don't knock the 350TH trans. I think its the best trans ever built. I have one in my 79 Camaro with over 300,000 miles on it and the only thing that has ever been done is changed the fluid. I also have had one in a pickup with over 400,000 miles and the same story. There are lots of reasons your buddy may not be getting along with autos. Auto trannys need more TLC and you can't jerk them around like manuals.

Anyway, if you're sure the tranny is properly rebuilt with good parts, your likely problem is a missing or cracked vacuum hose. Check for bad hoses and replace any questionable ones. I have had cracked hoses make my trans act up before.

[84 silverado]

it may be just a stupid idea but by some chance are you mistaking the converter lockup for a gear change? On some vehicles the lockup is very pronounced and actually feels like another gear change but only drops rpm about 200-500 rpm's(depending on the converter rpm) Just thought I'd ask because a th350 is normally not going to drop a gear unless it's smoked.  

[76L88]

Does it have an adjustable modulator?