Klaus, there may be a million reasons, I think for the malfunctions there, but I think we always start by checking simple, non-expensive things. Just please bear in mind that these automatics work when everything is in order (as it is all interrrelated) - linkage, vacuum, ignition timing etc.
Here is a passage from Joe from Technical Manual:
"Trying to help my mechanic here with any of your great ideas. Presently we seem to have all sorted out with the transmission, but we can't get the kickdown to work. We discovered a broken wire which prevented the relay from letting the kickdown solenoid on top of the tranny to work; now that is all working, but still no kickdown. His next task is to remove the solenoid (remember it is working) and try to engage the kickdown manually from the top of the transmission while the car is in motion. Anyone have any ideas on this? Can the transmission seemingly work fine (shifts pretty nicely), but no kickdown working internally? As I mentioned we do have the solenoid and kickdown circuitry working, and we think there is enough travel on the solenoid as well. Any assistance would be appreciated.
Joe Alexander: you can remove the access cover on the passenger side tunnel area and observe the movement of the transmission linkage and three position solenoid, while test driving the car. You will need a second person and a flashlight. The kickdown or passing gear switch on the floor under the accelerator pedal must be engaged and working to activate the solenoid. When fully depressed this switch is engaged and it energizes the three position solenoid which will move the control pressure linkage on the side of the transmission. This linkage changes the control pressure at the modulator assembly on the transmission and causes the downshift. Make sure you have power going in and out of the accelerator kickdown switch when it is depressed. Next try observing the operation of the three position solenoid. Position one at idle in gear, position two after driving off, position three at full throttle (accelerator fully depressed and switch engaged). If all seems to be working ok then more complicated adjustments can be made at the modulator or the linkage on the transmission (do this only as last resort and after everything else is checked out). Let me know what you find. Good Luck, sounds like you are getting close.
I finally got a call yesterday from the mechanic, and my car is done. Turns out that the transmission passing gear issue was, and many of the "clean up" and "sorting out" issues he discovered were matters of adjustments as I thought. In the initial case of the kickdown issue, 1st there were wiring problems, wires on the tranny were in the wrong place. 2nd, there was a broken wire on the harness at the relay. When those items were repaired, then the solenoid was able to work. Manually, they were able to get the kickdown to work; however the solenoid did not give enough travel in order to activate automatically. They tell me that the final resolution was linkage adjustment AND a bent "rod". When they straightened the bend rod (I think this is that the solenoid pushes on in the tranny) and adjusted the linkage, voila, it all works."
Perhaps also you may check this voltage topic, you say you had 10.8V. Was this with the engine running? I am not sure that the 3-position solenoid will work properly at 10.8V. You need more than 11V.
