Chrysler Repair: Transmission rebuilt but still not working: Dodge van 3.3, dodge grand caravan, dodge van

Question
Ok sorry about not giving the year model.  I have a 1990 Dodge Grand Caravan SE.  3.3L A604 Trans.  Today the transmission shop states the error code is 42.  This did not make sense to me.  I also insisted that they flush the system and put in ATF+3.  They think they have a bad TCM.  The are picking up another TCM tomorrow.  Any help would be greatly appreciated.  3 Days now....I gotta get my vehicle back.  Thanks
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-----Question-----
Rebuilt Transmission, 3rd time transmission shop has replaced it within the last 2 months.  TCM replaced twice, valve body replaced 3 times...still same problem.  Just out of the blue you can be driving down the freeway and the van moves into neutral.....put the shifter into neutral and turn off the ignition and back on again and the problem is corrected also sitting in traffic moving either very slow or stopped with foot on the break the transmission shifts into limp mode.  Turn off the ignition and back on again and works fine.  Transmission shop does not know and I am trying to figure it out.  I have replaced most of the sensors...YEA thanks to one of your other experts my cruise control works after 2 years being broke.  Anyway my next move is to install a ECM and see if this problem goes away but I don't think it will.  Any ideas?  Also what type of transmission fluid should this have been charged with?  They put in Dextron, but I have been reading that this is a no no...

-----Answer-----
Hi Ed,
Dexron fluids are NOT RECOMMENDED for the electronic transaxles of Chrysler. They recommend ATF+3 (MOPAR 7176) at least thru the '99 models. I can't say for sure about later models than that. This seems to be a very important point so I believe that all the Dexron should be removed if you are to have a hope of getting long term service from this rebuilt unit. That means a power flush, not just drain and refill because only about half or less is changed out by draining the main unit. The fluid in the converter and heat exchanger and tubing will not drain via the pans.
On the various behavioral problems, have they used a DRB II (vans thru '95) of a DRB III (post '95 vans) to query the TCM memory for fault codes? Everytime it goes into limp mode a fault code should be set in the memory. That is the most efficient way to diagnose the problem. Because this appears to be somehow related to shifting into neutral on its own, I wonder if the switch inside the valve body that is supposed to sense the position of your gear shift lever is not making contact internally to form a positive circuit or if the shift lever cable is adjusted properly so that the position requested is actually being chosen. You didn't mention which year you have, so this may or may not be relevant, because the shift position indicator is electrical on the newer models and depends upon the internal switch located at the bottom of the shift "tower" shaft. But that might be the simplest reason for what you describe.
I would certainly though want to get a fault code readout with the diagnostic readout box (DRB) that is appropriate for your year of van.
I doubt that the ECM is related to the problem, but the DRB readout would likely tell you if that was the problem or not.
If you can get any fault codes out, write me back and tell me the year of the van, and then we can check for what those codes portend. Get the numbers and the names for the codes.
Roland

Answer
Hi Ed,
The code 42 is related to the 2/4 solenoid ciruit (a failure of the periodic test of each of 4 different solenoid circuits for continuity, in this case the solenoid for the  2/4 clutch).
The possible causes are: open or shorted 2/4 solenoid driver
circuit(red wires on 16, 17 should be continuous to white on 19 if solenoid has continuity), open power ground circuit, problem with the 60-way harness/connector to the TCM (16,17,19;57,58 are grounds), problem with the 8-way harness connector of the solenid pack (4 should be continuous to 8), solenoid pack internal problem, or internal failure of TCM. Such a failure of continuity does result in setting a limp-in.
So if the TCM doesn't fix it, then checking the solenoid pack and the wiring harness wires for that 2/4 solenoid would be in order. I can xerox and postal mail you the specific electrical troubleshooting tests for the code if needed.
Roland