My TH350 is sticking into first gear. I've only driven the car maybe 15 miles since I installed the used engine and transmisson. the first few drives up the street it shifted fine and didn't seem like anything was wrong. Then it wouldn't go into 3rd but had 2nd, now it only sticks in 1st. Me and my mechanic buddy took it for a ride and managed to get it into second and 3rd, but we had to rev it sky high. His opinion is that something is sticking in the valve body which is causing it to not shift, which makes sense because it holds the higher gears if it actually gets to them. Any input would be helpful I have no idea what I am doing when it comes to the internals of a transmisson.
i would first check to see if it has a vacuum leak.Then pull the vacuum line to see if oil comes out.If not,then you need more advice than i can give-if so replace the modulator.My 2 speed 300 trans had a plugged vacuum line and would not shift out of first.Good luck.
Yes, vacuum modulator vacuum leak, or check that the kickdown cable isn't pulled all the way out and jammed in that position. There is a wire link that the cable eyelet hooks onto. Sometimes things get bent and jammed. Make sure you can pull the cable out, and it returns. The cable should reach full travel at WOT, if it is adjusted right.
Shortly after I drove the car when it was shifting fine I found the vacuum line was disconnected from the modulator. Can't figure out why having it hooked up would cause it not to shift, technicly it shouldn't have shifted with out it. The cable moves freely back and fourth, unfortunetly it's not hooked up due to my engine not having the bracket (odd since it originally came with a TH350) On Th350's in the past when I have had the detent cable unhooked and fully retracted the tranny just shifted sooner. Also I have a 1980 TH350 that I could pull a modulator off for testing, would it be roughly the same to install on the 1971 TH350?
all th350 modulators are the same. i prefer the adjustable ones you can get from most part stores. off the shelf b&n makes em for $10 or so.
Transmissions do get dirty and get varnish deposits, has anyone here ever put a product called KW TransX in a trans. I've driven many old high milage cars that have had lots of different shifting problems that I have used this product in and it has eliminated the problem in most cases. Clean and simple to try and if it doesn't work your only out eight bucks and your time. There's some in my high milage 350 turbo behind my 455 right now and trans still works fine. :bglasses: We need one of these smiley faced guys with his fingers crossed. Dave B
The THM350, and 400 for that matter, rely on 3 inputs to determine shift point and feel. Vacuum Modulator (engine load), governor (Engine RPM and road speed), and detent position (kickdown and throttle position). If you want your transmission to shift correctly, you have to have all three inputs connected and functional. Leave one off, and the transmission won't work the way it is designed to.
Well this morning I took the modulator and governor off my parts TH350. Since the car is still sitting at my mechanic body's he is going to try installing them and see if it makes a differance. Keith, I didn't know the detent hooked to the pedal on the Skylarks. The 71 350 and TH350 are now sitting in a 84 Cutlass, so I will have to figure out a way to hook the detent to the carb, I did steal a bracket off a early 80's Chevy 305, hopefully I can modify that to fit. We'll see how this all goes, hopefully something will work out, I don't have the cash for a tranny replacement or rebuild at this point. Thanks for the help guys!
