bicylindrico

If so I would like your input.

1997 C230. Owner was driving from Texas to Canada when transmission quit responding. No limp home mode. Just like neutral any any selector position. Found trans overfilled approx 4 quarts. Typical implausible trans ratio faults. Fluid clean. Speed sensors in actual values show N2 input about 50% of turbine speed in either S or W position and N3 at 0 rpms regardless or S/W position.

The owner was given possible scenarios and potential costs to fix vehicle and he decided to sell vehicle and he had been planning to sell the car soon anyway. He took a plane flight home and I now own this car. It has 180,000 miles and appears to have had a decent maintanance history.

I installed a used conductor plate from a mechanical failure tranmission and have the exact same input values but....after filling the transmission with new fluid at the correct level, the transmission began trying to work after fully heated and much revving and selector movement. It will now engage after bringing the rpm's up some and kind or bang into gear in forward or reverse. If the trans is in drive it may start in 1st, second or third and may shift or just hold that gear. It is very random. I also noticed the "desired" and "actual" inputs in actual vaues was typically incorrect for gear selection. Park and neutral was typically correct but reverse was always R2 and drive would sometimes not register at all or be incorrect in the "desired" field. I just installed a new selector switch in the shifter assembly. No change.

I am a person that has a hard time believing there is more than one failed component when something doesn't work but this has me scratching my head. I am suspecting a possible module but after finding the overfilled level, I keep looking towards something in the transmission itself. The module is also $700 my cost and an expensive guess. I considered a possible supply pressure issue but once in gear the trans holds strong and I couldn't find test instructions or values from Benz.

Any ideas guys? Thanks!

tbenz

have you ck to see if there is any trans fluid in the control unit, also are you able to read the adaptation values, has the trans been repaired before, it would be unusual for a trans with 180,000 miles to have clean fluid and no clutch material in the pan just from normal wear and tear

bicylindrico

Yes, I already checked for the fluid in the connector scenario. The trans fluid was not new but there were no signs of large debris in the fluid. That's what I meant by "clean". It has the normal orange/brown tinge the fluid always turns to and some normal clutch material at the bottom of the pan. The fluid is not original though and aparently has been serviced at some point. The adaptation values are in line and the owner had no problems with the trans prior to the incident.

I am leaving for a three day suspension class in Schaumburg Tuesday and will talk to the guys at school to get some ideas and input. I just keep thinking it may be a sprag clutch or something simple. The inputs for N2 and N3 should be a clue for someone in the know.

Thanks for the ideas tbenz and I will let you know what fixes the car.

C32AMG/02

Transmission RPM (N2/N3) sensors, wheel and engine speed sensor are input signals for the TCM, and CAN connected. With implausible input signal codes,TCM defaults to a variable substitute value, with loss of one rear speed sensor input, Check all modules for any fault codes. . Early years 722.6 had a problem with pressure regulating valve spring breakage. Symptoms were, delay into gear, and slippage.


Which fault codes were stored

benz-tech

not to oversimplify, but turn the headlighs on, and check the indicator in the shift lever area. the "D" should be lit if you are in drive. If not, it can cause no movement and/or limp home function. in that case the failed part would be the selector module (floor shifter assy). 98 and later do not have this same issue with an ESM.
its worth a shot.

bicylindrico

In case anyone is interested in what fixed the car....I disassembled the valve body last week and found two very small pieces of black plastic in two of the plungers just below the manual shift valve. The transmissin now operates just fine and I have had no issues since.

I was not able to find any broken areas on the original conductor plate so I do not know where the plastic came from.

I condemned the trans or internals because the transmission would not respond to selector input with all electronics disabled(module unplugged). The manual shift valve should allow for 2nd gear and R2 functions reguardless of any electrical input. This trans was just as erractic when the module was unplugged as plugged in.

I hope this may help someone with trans troubles in the future. The module will need to stay plugged in to allow the vehicle to start though. Just unplug when running. Good luck!