- CHEVROLET TRANSMISSION VACUUM MODULATOR MOD
- CHEVROLET TRANSMISSION VACUUM MODULATOR DRIVERS
- CHEVROLET TRANSMISSION VACUUM MODULATOR FULL
Adjustment or replacement of the vacuum modulator can be used to adjust the part-throttle shift points. When there is engine vacuum on the modulator, the hydraulic pressure to the governor is reduced, and the governor finds it easier to overcome the hydraulic pressure to open the shift valve, so earlier shifts are selected.
CHEVROLET TRANSMISSION VACUUM MODULATOR FULL
At wide-open throttle (low vacuum), the full hydraulic pressure is provided to the governor and the wide-open throttle shift points are selected. The vacuum modulator adjusts the hydraulic pressure to the governor dependent on the engine vacuum. Adjusting the governor weights and springs can be done to adjust the wide-open throttle shift points of the transmission. There are flyweights and springs on this spinning widget, and when the flyweights overcome the springs and hydraulic pressure, the flyweights push open a rod valve that lives in the center of the governor shaft. It is a little widget that spins with the output shaft.
CHEVROLET TRANSMISSION VACUUM MODULATOR DRIVERS
The governor lives behind a cap secured by a bail on the drivers side of the transmission in front of the tail cone. All stock TH350s were manufactured the same their differences in shift characteristics for specific engines and vehicles were set with the governor and modulator. It's the inconsistancy that bothers me.The vacuum modulator, together with the governor, controls the shift points on the TH350 transmission. Oh, I've been looking into the shift firmness, the faster the shift the harder it typically is, so if you want a smooth soft shift and not a snappy hard shift then you want to slow the shift down, the modulator should change the speed at which it shifts (the one I'm buying is +/- 4mph) it's the internals that change the harshness, odds are the trans got a shift kit put in to increase performance and longevity, the down side for you is snappy hard shifts. How late has it been shifting? I know when it's colder out my truck will shift at pretty high rpm if I get on it at all and I can smell burning oil, maybe you're burning a little oil on that bank? maybe the high rpms all the time are just too much for your rings (maybe worn out and letting oil blow by into the cylinder) What color smoke is it and what does it smell like? It could also be fluid got on the exhaust which would make it smoke at that area, unless there's a hole in the pipe, a substantial amount of fluid on the exhaust can smoke for quite a while. I don't see how fluid would be pulled through the vacuum line so easily though, I would think the vacuum part of the modulator would be sealed from the rest so that couldn't happen. Would i be correct in assuming that my valve behind the modulator is stuck? this is the only conclusion that i can think of.Ĭorrect me if I'm wrong but the vacuum line should go to the manifold vacuum port on the intake, which should be drawing vacuum from both banks, in which case if you get trans fluid in the engine from that it'd be from both pipes. but after i removed it again about 3 hours ago and stuck my needle nose pliers in there to pull the pin out i hit it and then a driping stream came out, maybe a couple oz's of fluid then it stoped.
CHEVROLET TRANSMISSION VACUUM MODULATOR MOD
also when i replaced the mod this morning zero trans fluid came out, even after driving it to work (10 miles) and back, i removed it and no trans fluid. ive read somewhere on another forum that the rod behind the modulator in the transmission should be able to move freely back and fourth opening and closing the valve, well mine doesnt move at all. Ive check, and there is vacuum at the modulator, about 15-20 at idle. Turned the screw all the way in, still shifted at high rpms and shifted very hard. Turned the screw in halfway where the old mod's screw was, shifting got lighter but still shifted at high rpms. So i turned the screw out all the way, nothing still shifting really high and still shifting hard. i was told from my buddy out west that if you turn the screw on the nipple of the modulator all the way out that you would have very fast shifting and it would be very soft, and if its all the way in it would be long shifts and it would be very hard. So i went to adjust it and it didnt do anything. I just replaced my Vaccum modulator to fix a shifting problem and the old one had a bad diaphram, I figured id start a new thread on this subject since its diff from my old thread.