Chrysler Repair: Auto trans limp-in: codes 731,732, 733,734, gear ratios, best bet

Question
Hi Roland, I have an issue with my 99 sebring transmission. I've seen similar Q+A's on it, but nothing that has helped me, so here's the skinny- From what I can tell its in "limp mode" because it's stuck in second gear (again,... I'll get to that shortly). It did this and the light came on, codes 0731, 0732,0734 and lastly 0700, all incorrect gear ratios followed by a "malfunction" code. Trans shop said that when they do this they are shelled, and best bet would be for them to install a used one, about $1300 trans and labor. (I had reservations about this scenario, being why not rebuild it, after that is what they do, or is it cost prohibitive, or are they pulling a fast one). any ways I replaced it myself with a used one and test drove it 5-10 miles. It worked beautiful, like it should, problem solved. Pulled into the garage to check fluid (+4 type) one last time, it was fine. After about 1 hour I went to run errands and not even 2 blocks later coming to a stop sign, it dropped down a gear (kind of hard and abruptly) and now is back in limp mode, just like the other was running, and again, the similar codes, 0731, 0733, 0700. I cleared all codes even before removing the first trans, so are both shelled? or is it elsewhere?

Answer
Hi Chris,
Those codes of course refer to gear ratio errors which may be real due to slipping clutches. Because the replacement was used and may have been why it was in a wrecking yard, it may very well also need to be rebuilt. The manual suggests that before concluding a rebuild is necessary that you do the following:
check the wiring from the trans to the trans controller
do a shift lever position test
measure the clutch volume indices and compare to spec
do a 1st gear clutch test using a Diagnotic Readout Box to monitor the slippage
It is always possible that the input or output speed sensor is bad, though there is usually a code for that, and those sensor readings are the basis for the fault codes and limp-in assignment. You might try switching out the sensors if you re-used the old ones on the 'new' transmission.
Unless one of those comes up with an alternative reason, then a rebuild is necessary.
The rebuild is in the range of $2,000-2,500 I am told by others. So finding a used one with a known normal function at the time of removal would be a reasonable alternative. But verifying that fact is the problem.
Roland