i have a th400 that has been rebuilt and has a 3800 stall in it, the trans shifts fine from 1st to 2nd, but will not shift 3rd unless i let off the throttle and get back in it. i dont have a problem on the street, only at the track at wot.any feedback would be appreciated. thanx
How about the detent solenoid? If it is stuck in an open position, it won't upshift. Constant 12 volts to the solenoid? But then you said it will shift if you let off the gas. The only other thing is the vacuum modulator. Do you have a good leak free supply of vacuum to to the modulator? Are you using the steel line? What vacuum does the engine make? Make sure there is no ATF on the vacuum side of the modulator. If there is, the diaphram has a leak.
think we solved the problem,the spring for the 2-3 shift was to tight,so we took 2 rings out.trans feels better on the street,now just got to get it on the track.thanx for your input larry. :beer :beer
