QuestionHi. I have a 1993 front wheel drive town and country v6 van. Now and then the transmission will drop into low gear and stay there. manual shifting of the trans. doesn't effect this. If your shut the car off for a couple of minutes, it will run normally again. The problem does not seem to be temp. or speed sensitive. A local trans shop replaced the speed sensor module. Still does it. Any suggestions? Thanks.
AnswerHi Steve,
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. It is called "limp-in" mode.
Have you been told by the trans shop whether there has been 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?
The chances are there is 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 worth spending about $50 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. So a dealer or a competent independent transmission shop (but NOT a franchise type like Aamco where the usual answer will be to do a "rebuild") with a reader for Chrysler transmissions should be able to do that. Ask for the code number(s), what they mean, what repair is needed and how much it will cost. Be sure that they have the 6-pin ("bus diagnostic connector") reader plug adapter that will give them access to the memory via the port under the dash. This is NOT the same plug as is in the engine compartment (which is also a 6-pin plug but arranged in a different pattern) for accessing the engine controller memory. Their reader also has to be equipped with a program (cartridge) that accesses the transmission computer. A Chrysler dealer will have this device called a DRB II.
Then write back and we'll evaluate what you were told, particularly what are the fault code numbers. I have the '93 factory repair manual and can look up what the numbers mean and what needs to be done to fix this.
You don't have to authorize a repair until you decide you understand the situation, and maybe get another repair estimate. You might even ask before they do the readout if in the case you decide to authorize the shop to do the repair "will the cost of the readout be credited against the cost of the repair"?
So take your time with this so you don't do any more unnecessary repairs. The cost of a rebuild is high so getting a second bid is worthwhile and also comparing warranty provisions is wise if that is the diagnosis.
But that readout is the only way to avoid doing the wrong repair.
Roland
