Hello everyone,

I apologize in advance for the length of this post, but I feel that it is necessary to illustrate exactly where this problem has led me to and why I'm stuck.

The car: 2001 SL1 TAAT automatic transmission 83k miles.

History: I tracked this car down three years ago for my girlfriend to give to her oldest son for his first car. I live in Indianapolis. She lives in Illinois south of Effingham. To put the car even further away, her son is going to college in Carbondale, IL. The car has been brought back to Her house and I have been working on it, but every time I try something else to fix the problem it's a 4 hour round trip. I'm getting tired of guessing.

The original complaint was the car was not wanting to go into third gear, and was bucking/slamming. Reverse was never a problem.
Research pointed to the valve body. Visual inspection showed no burning or indications of the wiring harness failing. The fluid looked good and clean, and smelled normal.
I replaced the valve body, and the attitude of the car changed. It seemed to start off slowly, and it would occasionally slam shift. Again, reverse acted completely normal.
After coming back from the test drive I pulled transmission pan back off and retested the solenoids which all test normal. Post mortem on the old valve body revealed a bad third gear solenoid.

Observation of the car has shown it is starting out in third now. It slowly drags itself up to speed and only shifts once. trying to manually shift it back down into third or second with the gear selector doesn't work. I will not respond.

The next possible solution I was pointed to was a possible loose input shaft nut. That has been tightened to specifications, as well as the output shaft nut. The fluid and filter were changed at the same time for good measure. No change in the car. I can not find any evidence of actual damage or contamination. In addition, every major ground I can locate on the car has been cleaned and tightened.

Further research indicates that in order for first gear to engage, the solenoids for second, third, and fourth must all be energized. Logic is telling me that if the car is starting off in third, that there's a problem with the circuit for the second gear solenoid. Am I crazy or just confused?

The car is in a town with very limited options for professional service. There is no specific transmission shop. It was taken to the only mechanic in town which gave it a blanket diagnosis after a test drive of "it needs a new transmission". I disagree due to a complete lack of evidence of damage.

So, first I would really appreciate any other opinions. Secondly, I am looking for specifications for the wiring harness as to what the wires do and what they should read for voltage. I really feel like this is a wiring problem.

Thanks for your time,
Chris

 

Have you tried swapping the apparently "not bad" solenoids from the original valvebody for first and second into the new valve body.
Usually the S cars will throw "incorrect gear x ratio" P codes when crap like this happens.
The shaft nuts are meant to be used once and commonly will back off again after retightening. Not the next day -- just FYI

II know I saw something on youtube that exactly answers your questions and also shows exactly which solenoids are involved in each gear.

You sound quite with it but never hurts to ask: Have you verified continuity between the electrical connectors on the valvebody and their connections to the solenoids?

It also sounds like you might be able to just switch out the 3rd gear bad solenoid with a new one and try the old valvebody. Sounds like there were no internal electrical issues with that one

 

Yes to the above. I forgot to mention in my original post that the new valve body came with updated Sonnax solenoids. They all check out, however during a subsequent disassembly to try to figure out the continuing failure the solenoids were all moved to different positions. No change in the car's behavior.

The buss plate that connects the wiring harness to the solenoids was also swapped out with the original one, and no change in the car. Both the original and replacement were checked for continuity and passed.

The range selector switch has also been eliminated as a cause. You might be beginning to see the root of my confusion here. All of the usual suspects have been eliminated one by one. I'm out of horses and zebras, and now I'm hunting unicorns.

 

 

one thing I don't see mentioned in this thread is whether or not that wire like linkage is intact and correctly connected. It can slip off or get missed during removal or installation of the valve body.