Question
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Followup To
Question -
I have a 6cyl 1991 Lebaron that often won't shift up when accelerating. I think it is a 4 spd automatic (P RND3L). When it doesn't shift up if I stop, shut it off and restart it will shift properly. Lately it has not been shifting even after restarting. It also shifts into Drive roughly when first starting out. I have drained and replaced the filter 2 times in 3 years but this last time I saw no improvement. Also the speedometer will sometimes not work when starting out but then start working later. Could these problems be related? Could a sensor on the transmission be the culprit? If so, which sensor should I look at first and where would it be located. I can't afford to put a lot of money into this car, so any assistance will help. Thank you.
Answer -
Hi Garry,
The sensor on the output of the trans does factor into the control of the trans, but not the speedometer which was still driven by a separate sensor on the top of the transaxle extension housing (the part of the trans from which the half shafts extend)in the '91 model. Later years dispensed with the latter sensor and drove the speedo off the output sensor. The speedo sensor can be damaged if the right half-shaft is removed from the housing without first removing the sensor.
The output sensor is located on the side of the trans that faces the front of the car, at the very far end of it, about midline. The input turbine sensor is on the same level but at the opposite end of the trans. Both are used in the control of the trans, but there are many possible reasons for what you are experiencing. 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.
What would be useful 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.
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 readout 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
Roland,
The codes that we got when we hooked it up were:
53 - gear ratio error in 3rd gear
36- fault immediately after shift
51- gear ratio error in 1st gear
I have no idea what these codes imply. Hopefully the problem is not too major. I really appreciate your assistance.
Thanky you,
Garry
AnswerHi Garry,
The codes are helpful but not definitive as is often the case. The 36 says the turbine vs output shaft speed errors (51 and 53) are detected immediately after the shift attempt, and that eliminates the possibility of an electronic control problem. It tend to point toward some internal mechanical damage that means a rebuild at a cost of about $2k. However, it is also consistent with a few hydraulic-only problems which in light of the age of the car and your budget would be worth considering for a repair attempt (though you can see what the shop(s) say when you propose these as an alternative of going directly to a rebuild or giving up):
internal solenoid leak
hydraulic pressure too high
valve body leak
faulty regulator valve
stuck/sticy valves
worn pump
and the traditional:low fluid level, or faulty cooling system which would be obvious if present.
All of the alternatives involve only the valve body or associated hydraulic system which can be seviced without removing the transmission from the vehicle. The question would be how much $ to go thru the list to determine if any of those are the answer or not? And what are the odds, based on the codes and mileage, that you might avoid the rebuild/abandon route by investing in that effort?
I can't answer those questions, but a competent trans shop or dealer can.
The 51 and 53 say there is slippage while in first or third gear, but don't say exactly why, unfortunately.
I would be interested in knowing what they say, what you decide to do, and what is the result.
Thanks for letting me know, in advance.
Roland
