I just bought a new th-350 to back up my hemi. It came from a reputable shop that has been around for a decade or so. I installed it and hooked the vaccuum modulator up. Shifter is a Hurst Quarter stick. Motor is a 10.5/1 331 hemi thats built pretty well. Heres my issues: without vaccuum modulator hooked up 1. Putting the transmission in 1st from neutral or park it runs up to about 2500 rpm and autmoatically shifts to second. 2. After running it throught the gears down the street I come to a stop and the transmission shifts down to second but not first. with vaccuum modulator 1. the transmisson shifts from 1st to drive when the shifter is in either 1st or in drive within the first hundred yards or so. I talked to the shop that built the transmission and they want me to drop off the whole car. I really dont want to leave my car with anyone Bone Head mechanics, expensive parts, freshly rebuilt hemi etc... so I am hoping for an idea of the issue or a fix
Does it have a shift kit in it? if there is any dirt or miss placed ball it won't shift right for anything in the world. But the vacuum modulator makes me think its something else. If you think that you can trust the shop take it down there, hopefully they will fix it and set it strait. Otherwise start messin'.
The vacuum modulator controls "throttle" pressure, and basically sets a pressure that has to be overcome by another hydraulic circuit controlled by road speed. If you're shifting too early, it could be because throttle pressure is too low (make sure you're on manifold vacuum), or because you're running a low-ratio final drive, small tires, etc. That said, most vacuum modulators are adjustable. If yours isn't, you can probably buy one (take the hose off, if there's a slot on the nipple you can adjust it). Try adjusting it yourself and go for a drive, you might not have to take it to the shop.
if the above advise doesnt get it.. call the shop that did the work. set up an appointment where you can baby sit your car while they get the job done..If they are a good shop, and stand behind their work, It should be.."no problem". I would make it Chrystal Clear you are NOT leaving the car for them to work on it when they have time, you want an appointment for it to be seen and fixed. Isnt there also a mechanical governor on TH350's? if they dont have a build kit in them it should shift on the mechanical govenor..but usually very late.
The Jalopy Journal
