Chrysler Repair: DTC P0750 in 2001 Dakota, solenoid pack, speed sensors

Question
Roland,
I've been having intermittent problems with the transmission in my 01 Dakota, 4.7L with 45RFE.  It keeps going into "limp in" mode and giving a code of P0750 L/R Solenoid.  I've replaced the TCM and input & output speed sensors since they were easy to access, but that didn't help.  I was going to replace the solenoid pack, but I've read through other answers and have noticed that isn't always the issue.  I want to make sure I'm right before I spend the money on a solenoid pack.  I've been doing some research and noticed that Chrysler upgraded their solenoid packs from a black plug connector (P/N: 4799934AD) to one with a white plug connector (P/N: 68002342AB).  Do you know the reason for the upgrade and what kind of issues they were having with the black plug unit?  Also, do you know the procedure to diagnose and fix the issues I'm having?  I'm a do-it-yourselfer with some mechanical knowledge but I'm no mechanic.  How would I test the circuits for the L/R solenoid?
Thanks,
Dennis

Answer
Hi Dennis,
I don't have the wiring specific to a Dakota trans but the L/R circuit is basically 2 wires: a yellow orange common 12V supply to pin 4 of the assembly at the trans (which supplies all the solenoids) and a dark green/white on pin 7 that goes to pin 20 of the TCM. Those wire colors are from the '02 minivan; your colors may be different but I believe the pin assigments are correct but try to find a wiring diagram for your truck. You could check that the wires are patent and are not shorted to ground. You also might try switching out the transmission control relay, if you find another one in the power box with the same part number that is not crucial to operation, as if the contacts in your present relay were burned that would cause a failure of the trans to operate and be 'seen' as an L/R failure. If those all show OK, then you pretty much have done everything except replace the solenoid. So do the checks that I listed before doing the pack. I don't have any knowledge about the change of plugs.
Roland