In my 71, I have a BB th 400 with switch pitch 4000 convertor, manual/ auto transgo kit and 34 element sprag, big clutch pack with no waves, but used paper clutches, GM bands and GM seals this time. Last rebuild was over 10 years ago and it had held up well to a previous 500 hp combo. First time out this spring, did a couple of hard street runs and everything was Ok as usual on the upshift. Then cruised, slowed down and dropped it into 1st while still moving and did a rolling burnout and kept driving. When coming to slow down at the first intersection, noticed that there was a 3 second delay into second. Then starting from stop again (I manually shift through the gears) and no upshift into first or second. Reverse seemed to apply a little harder even in high stall mode. Limped home in 1st, which was only a hundred yards. What gave up? Seal, Band, sprag??? I heard that a downshift driving into on the TH 400 applies a different combination of bands and cluthes than running it up from a standing start. The stopped 1st gear starts are preferable for taking extra abuse. I went with the GM stuff because of the previous poor quality of the offshore maufactured seals that were supposed to be trick. What is everyone using now for high HP ? Next motor will be between 600 to 675 Hp. Tom
i assume the fluid level is good ?does it smell burnt? when did you change filter last?check the vacuum line. i have seen the governor gear break off before(its only plastic) i would drop the pan and take a look inside.what is in the bottom of the pan and a look around might tell ya whats going on . since it looks like you got to drain it anyways.
The car sees limited mileage, but it is mostly hard. Fluid does smell good, and level is Ok. Further, I have a deeep truck sump. Prior to rolling drop shift, the trans shifted as crisply as it always did. The one thing I didnot mention was was that the valve body had a shift problem when it was first built, but on dissassembly & re assemby of the valve body spools & pieces it worked fine. I'll drop the pan. Tom
Will it upshift manually on a full-throttle shift? Check for vacuum at the modulator, and also check that the modulator didn't get a leak. You'll only have high-RPM upshifts if the modulator isn't working. At least something easy to check before pulling the pan.
