TH 400 problem
Thread Starter
Racer
Joined: Jul 2007
Posts: 269
Likes: 0
From: WV
TH 400 problem
I installed a TCI valve body last spring and have been chasing down problems with the tranny ever since.. The car runs amazing around town but when driving for extended periods of time over 55 the tranny does not want to go into third gear until the car hits about 3800 rpm and then falls out of third as soon as you drop below 55... It only does this after driving it a lot any clues
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Check that full intake manifold vacuum is going to the vac modulator and that there are no leaks in that line. You might also replace the vacuum modulator.
If the shifts are very firm, the above is probable, but if the shifts are relatively soft, check the governor flyweights and springs. Cut down weights will raise the shift points. Also check for excessive clearance in the governor bore - could be a worn gov bore or worn lands on the gov itself.
Another problem could be that the detent regulator in valve body is continually held by a stuck valve, or by the detent regulator solenoid. Check that 12 volts only goes to the connector on the trans when the kick down switch is activated.
Good luck!
If the shifts are very firm, the above is probable, but if the shifts are relatively soft, check the governor flyweights and springs. Cut down weights will raise the shift points. Also check for excessive clearance in the governor bore - could be a worn gov bore or worn lands on the gov itself.
Another problem could be that the detent regulator in valve body is continually held by a stuck valve, or by the detent regulator solenoid. Check that 12 volts only goes to the connector on the trans when the kick down switch is activated.
Good luck!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
I think the rubber hose portion of the vacuum modulator line is getting hot, then collapsing so that vacuum no longer actuates the modulator. That line should be mostly steel with just short lengths of vacuum line attached to each end. Check it out.
