Hi,

i have a th350 transmission that is acting up... when i put it in drive it shifts right into it and drives fine, the same with reverse, but when i start driving it wont shift out of first.. i mean it pulls so strong and runs really good but it wont shift i dont think.. the car will keep accelerating to the point where the rpms get high and i let off the gas, at this point i can hear the car decelerating through my exhaust and when the rpms get low enough i give it more gas.. the car just picks up where it left off.. i mean its so fact and strong its hard to beleive the trans may be messed up but i wont upshift or downshift at all.. i can manually shift through 1,2, and drive and it still does the same thing... the trans does burn a little fluid but i check it regularly, i dont let it run low... what do you guys think? if this is something easily fixable thats great i dont really want to have to rebuild it if i dont have to...

Thanks

 

Most likely problem is the vacuum modulator - either the hose has been disconnected or the modulator is bad. Check the hose first, check for vacuum where it connects to the modulator at the trans.

Also, keep your foot in it and see if it ultimately upshifts. If the modulator goes bad or loses vacuum, the trans thinks you are at wide open throttle and delays upshifts to nearly redline.

 

i pulled the car around to the front yard...put it in park.. took the vacuum line off the modulator, its got plenty of vacuum, reconnected the vacuum line, put the car back in drive AND NOW IT WONT MOVE!!! LOL i have to rev it pretty high just to get it to move a foot... WHAT HAPPENED???!!!

 

Sounds like you need to verify the condition of the fluid and presence of it, then get a transmission pressure guage and check your line pressure in drive, and all gear ranges. If you are reading low pressures in any of the ranges you might have an internal leak from seals or the valve body. But before checking internal condition look for leaks in the vacuum line to the modulator(fluid may be present). What is the condition of the modulator itself, not the presence of vacuum , but the modulator? Test it with a hand held vacuum pump(Mityvac or equivalent)by applying vacuum of 20" for 30 seconds it should not bleed down within this time. Hows the filter? Is it clogged? If your fluid pressures are normal during your pressure check through all gear ranges then you will need to look inside.