Hey there.. I have a 1 year old TCI th350 (good for 450HP), and it's been working fine.. Until a few days ago, it shifted a bit later then usual, from 2nd to 3rd.. -Okay.. -no big deal ,but! Then at the freeway, doing 70, I had to ovwertake another car, -And PowWWWWW - My old heap sounded like a INDYcar, -w. 6000 RPM's ... It shifted into 2nd !! (I have 3.42 gears) :3gears: He looked a bit schocked, -and I proberbly did too.. -but as any gearhead, I didn't loose my cool... -I just thought 'the fk..nn trans is toast!!!..' -but it proberbly wasn't.. (I hope) As cool as that sounds (w. engine doing 6000 RPM'S on freeway), I still don't like the fact that I might blow up my engine.. -mind you, it pulls until 6400 or so, but still... :eek2: Do any of you guys have an idea what might be the problem ?? I know that a faulty modulator can cause a tranny to shift a bit later into 3rd. -but a way high rpm-kickdown also?? Any help is greatly apreciated..
If the modulator is reading too little vacuum when you accelerate slightly and the vacuum drops a little it will think you've got it floored and downshift. Do a quick check of the vacuum line that runs to the modulator to make sure its not leaking any, then check the modulator out.
On the THM 350, make sure your kickdown cable is adjusted correctly. The modulator you have, should be an adjustable one. You may be able to adjust the minumum throttle shift points somewhat (2-5 MPH). The adjustment is through the vacuum nipple. For later shifts, go clockwise, for earlier shifts turn counter-clockwise. Make sure, your vacuum supply is good and leak free. I'm assuming you have an accurate tach, so you know for sure what RPM the trans shifted at. The TCI 350 is a great transmission, I had one in a 72 Skylark, and was very happy with it. I'm sure you didn't hurt the trans. If you would like to lower the full throttle shift points, you can modify the governor with a B&M kit for that purpose. It takes alot of trial and error, but it is worth it, and the testing is always fun :Brow: :laugh: http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=15697&prmenbr=361
Well.. I did floor it.. -But still it shouldn't shift down into 2nd. (6000 RPM).. normally it would only shift down if I was doing 55-60, AND it didn't shift back into 3rd. untill I dropped the accellerator.. And I'm not too keen on trying to see at which RPM point it will, you know ? But you're right bout the vacuum line ofcause.. Anyone else had this 'experience' w. your trans ??
I quite like the 350 too.. The kickdown cable haven't been adjusted for over a year since I installed the trans.. And the modulator is actually in 'late shift mode' .. But still.... No changes made whatsoever and the trans is all a suddenly changing shift points -well I did install a 140 amp alternator lately... -Hmmm... :error: I'll check for leaks at the intake plus at the modulator (it,s a stainless steel line in the middle)
Take the modulator out, tilt the vacuum nipple down. If any trans fluid comes out it is toast. Make sure the modulator holds vacuum. Test it with a mityvac, or equivalent.
