Question-------------------------
Followup To
Question -
I have a 1994 chrysler concorde. v6 engine.On occassion after a 20-30 min. drive on the highway, the drive is fine , once I get off the highway, I notice that the transmission appears to be go in some sort of low gear and remains there until I shut the engine off,wait about an hour then the transmission feels normal again. I heard and read something about it going into a "limp mode". Can you explain what this is and how serious the problem with the transmission may be? What would my first step be to diagnose the problem I am having? I haven't had anyone look at the problem yet, I just want to investigate first, before I dish out money on someone that tells me I need a new or rebuilt transmission.
Thanks in advance
John Masters
Answer -
Hi John,
You are wise to get info about the trans before commiting to any repair because a "rebuild" is so expensive. Fortunately there is a self-diagnostic capability in the electronic controller of the transmission (which is a separate unit from the engine controller). What you need is 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. That exact lock up is what happens when the transmission computer notices something is wrong and so it protects the transmission by only driving in 2nd gear until it can be serviced so as to protect against any further damage. It is called "limp-in mode".
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.
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 had 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 a 5-pin plug) 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 '94 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.
But that readout is the only way to avoid doing the wrong repair. Good luck to you and let me know what you learn.
Roland
P.S. Also check the level of the trans fluid as it shows on the trans dipstick. That alone being too low will cause a limp-in situation. But only add Chrysler brand fluid if it is low, and don't overfill it.
Follow up:Jan 22,2006
I took the car into a Chrysler dealer and asked to have the transmission electronic controller read and explain any concerns. They seemed to know what I was talking about. After bringing it into the shop,they called me to the desk to tell me the diagnostics test gave them no codes but a readout as "fault gear ratio first gear ". After doing further investigative tests such as:"cltuch/pressure ratio" they explained that the problem is in the transmission seals and that it will need an overhaul. I asked them to explain what does it mean. They told me something about clutch pressures not being to specifications and bottom line is that the transmission seals are becoming hard and need to be replaced. Meaning that it requires an overhaul. I did not get any code readings as he told me the servive engine light did not come on during my problems.
My question to you.. Roland is : If there is a separate controller for the transmission , Why would they tell me that the service engine light did not come on for the contoller to record anything?
Am I really getting the run about from this dealer? Are there two controllers and are they separate from each other. They told me their cost to overhaul is about $2600.00, If I don't want to spend the money because of the age of the car ..just keep driving it until it stops.
If I have no choice and the damage is done ,is there any kind of additive that may soften the seals to prolong the life a little longer?
Paid them the diagnostic fee but not sure I got proper diagnostics?
Thanks,
John Masters
AnswerHi John,
Yes there are two controllers, one for the engine and one for the trans; and the engine controller will turn on the light, but usually the trans will not. While they may not have determined there to be any codes stored in the trans controller, their current reader may pick up the faults alphabetically, as it were, and state the problem that it has detected. The first explanation is a valid concept that says that the speed of the output shaft and the input turbine are inconsistent with low gear which could either mean that the low clutch is slipping or that the input/output sensors are problemmatic (but then there would likely be inconsistencies in the other gear rations too). The second term they used sounds like they did some valid testing of the clutch pressure on that low gear (either hydraulic or air pressure or both) and concluded that the unit failed to measure up to the necessary pressure levels (which implies a leak in the clutch seals). The corroborative fact too is that although the codes didn't readout (which is not always assured depending upon which fault and how often/regular it occurs), the trans is regularly going into limp-in mode as you described its symptom to me when you first wrote. You didn't say how many miles are on the trans or any previous repair history of it so I can't tell you if the failure at this point is typical, but given the age of the car, and if the mileage is over 100k, it is not unusual for these electronic transaxles to wear out around that point.
I haven't any experience with additives or heard of any positive results with same from other owners. I have heard that people who changed out the trans fluid have had some improvement in behavior. But to do it thoroughly you would want to have what is known as a 'pressure flush' because a simple drain of the fluid only exchanges about 1/3-1/2 of the total volume because so much is in the turbine and cooler which don't get drained if you simply drop the pans. I don't know the cost of that service. But check the fluid to see if it smells burnt or not. If it did, that would mean there is some slippage going on but also that the changeout of such fluid might well improve things for so more miles of service, but of course no guarantees of that.
It is unfortunate to be in this position of having such an expensive repair to keep it going. You might try an additive but I doubt that will help and may actually hurt.
So it is good that you had the diagnostic workup and that appears to me to suggest that you are close to if not at a rebuild juncture unless changing out all the fluid might buy some time.
Also of course is the question of a competitive bid from some independent shop, their warranty, and their references if you are given any to ask from people who have this Chrysler trans that they have rebuilt successfully. There might be a lower price reliable job that could be done that would be economically tolerable.
Feel free to write back with any information you get or have and want to share.
Roland
