Chrysler Repair: 1990 Plymouth Grand Voyager LE stuck in 2nd, plymouth grand voyager, diagnostic capability

Question
My 1990 Plymouth Grand Voyager LE is sometimes stuck in 2nd gear. When it is not stuck, it runs great, and shifts great. When it is stuck, I can put the auto transmission in Low, 2nd, or D and it just stays in 2nd. It does go into neutral, and reverse though. I can make it fix itself but I know what I do is not good for the car. I have to be going forward about 5 miles an hour, and pop it into reverse. THis usually fixes the problem. I found that on accident, I was putting it in neutral, once, and it accidentally went into reverse, and then it worked again for a week. It seems to happen more in the morning, after sitting all night. The fluid level is fine, no leaks, new transmission was put in 2 years ago (just barely out of warranty). I am hoping this is enough info. I want it to just be the linkage, but before I take it in, I want advise from you guys. I don't work on cars, and know very little. THanks in advance  

Answer
Hi Michael,
This behavior is programmed into the transmission controller so that when its self-diagnostic capability has detected a fault that could cause damage it will only drive in 2nd gear which uses a minimum number of circuits/parts. It is called "limp-in" mode.
I would suggest that you go back to the shop that replaced the trans and have them do a "readout of the transmission computer" which is an electronic test for the presence of coded numbers representing different faults that the transmission is experiencing at the time when it locks up into 2nd gear.
There could be some internal mechanical wear/damage to the internal clutches of the transmission, but because the cost of rebuilding is so high it is worth spending a little on analyzing whether that is true or not. It may also be the case that the problem is with electrical connections/computer or with the transmission fluid system (hydraulic) and those can be repaired without removing or rebuilding the transmission at much less cost.
In the readour procedure an electronic readout device is plugged into a port under the dash to access the memory and tell you the fault code numbers. It would be good to have this done just in case the problem has to do with the hydraulic or electronic parts rather than the internal mechanical parts because those could be repaired without taking the trans out of the car and dismantling it. Ask for the code number(s), what they mean, what repair is needed and how much it will cost. I would be very insistent if the period is just beyond the warranty that the warranty should be honored, even going to small claims court or making the moves to do that so as to get them to take responsibility. If they won't take responsibility then write back and we'll evaluate what you were told, particularly what are the fault code numbers. I have the '89 and '93 factory repair manuals and can look up what the numbers mean and what needs to be done to fix this.
So take your time with this so you don't pay for unnecessary repairs or repairs that they should ethically do under the original warranty.
Roland