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My ‘68 442 has a TH400 and best I can tell has no kick down switch. Nothing on the carb or under the accelerator. Not surprisingly it doesn’t downshift when I stomp on it. Where does the switch connect to the TH400 so I can verify it is missing? Assuming it is missing is there a kit to fit a ‘68?
Also, the tranny up shifts way too early. I don’t have a tach but even at wot I would estimate it shifts at 3000 rpm. How do you adjust the shift points? How is tranny supposed to hold shifts at wot (ie throttle position sensor, vacuum, etc)? Appreciate any input.
Thanks Joe. Just checked and connector on case is empty (No wire connected). Do you know if there are TH400 downshift kits or will I have to collect all the pieces?
I'm not aware of any "kit", since there just aren't that many parts and most people are going the other way (AT conversion to MT). The switch and bracket are available repro (these parts fit Chevelles - EVERYONE sells them), as well as a boatload of used ones for sale. The wire should already be in the car unless someone cut them. Even MT cars had the wires built into the harness and taped off.
If it shifts that early changes are there is something screwed up in the govenor. The detent switch is for a wot downshift. The govenor is behind a cover with 4 bolts on the pass side, it’s pretty easy to get to, and if you raise the rear of the car you won’t lose much fluid. Once it’s out, make sure the weights and internal valve move freely. Make sure the bore the govenor spins in isn’t scored, or the govenor itself isn’t chewed up. There are kits available to calibrate the governor, I would suggest finding a transmission shop and get a couple govenors to experiment with.
You can can also make MINOR shift point changes with the vacuum modulator. There is a small screw inside the vacuum line nipple, you can raise part throttle shift points 2-3 mph either way. Modulator adjustment is a fine tuning adjustment only.
Thanks Joe. Just checked and connector on case is empty (No wire connected). Do you know if there are TH400 downshift kits or will I have to collect all the pieces?
If the switch mounting bracket is still on the gas pedal mount, all you need is the switch and some wire. Go to your nearest parts store and get a lockdown switch for a TH400 equipped truck, it’s the same switch. One terminal on the switch needs to go to a fused power source, the other terminal needs to go to the kick down connector on the trans. As long as the solenoid sees power at wot the kick down should work. You MAY be able to hear the solenoid click with the engine off and with your ear close to the pan. You could also tune the radio to a empty AM frequency, you should hear a popping sound when the solenoid engages.
September 10th, 2018 | 08:04 PM
