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TH 400 transmision problem


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When i go from stand stil in Drive the transmission does a hacking after a couple of meters.
There after, no shifting problems.

So only in first gear, and only once after some meters, then no problems during driving.

What could this be?

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There could be a short in the kickdown switch wiring. The switch is on the carburetor. It goes to a terminal on the transmission for the kickdown solenoid; the other terminal at the transmission solenoid goes to ignition power. The wire is not supposed to move with the accelerator linkage. If it is touching the accelerator linkage, it can eventually get a worn spot on the insulation that occasionally shorts, pulling the transmission out of second gear into low gear. A scratchy connection can feel like a stumble.

If the wire is OK and closing the switch with your hand with the key on and the engine off produces an audible click from the transmission, the kickdown switch and solenoid are OK and the problem is a very likely a stumble in the engine, as Texas Jim says.

In my car, I floored the accelerator so seldom that the kickdown solenoid would stick. Once a year, when I tuned up the car, I would press the kickdown switch repeatedly until the solenoid freed up and clicked again. About three months later, I would notice that it was stuck again. So if you don't hear the click, press the switch about once a second for a minute or two and see if the click comes back.

If it's a stumble in the engine, and it happens once on a cold start but not thereafter, the first thing I would check is the adjustment of the automatic choke and the heat riser. If the heat riser butterfly is frozen (a common problem with all cars that use them), you will need penetrating oil, a brass mallet, and some patience to free it up.

In really old cars that burn oil, the heat riser passage through the intake manifold can fill with sludge. If this has happened, you will need to take off the intake manifold to clear it out.

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Hi, and thanks for your answers.
There is no stumble in the Engine, i'm sure it's the transmission.

I have no problem with kickdowns.

I have been suggested that the transmission don't build up pressure when I drive away, from stand still / idle.

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If I am not mistaken, there is a clearance spec for the band to drum clearance...

If that has increased over time, due to normal wear, it can be adjusted by a GOOD transmission shop... and I stress GOOD...

If I remember right, all you have to take off of the transmission is the pan. The adjustment is then accessible...

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