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I bought a 2003 c240 4 matic for very cheap .Seller said It just went into limp mode so I was pretty sure it would be the conductor plate .I changed the conductor plate on my e430 so I am familiar with that procedure .So... When I drained the att on the c240 it didn't look good at all .I didn't necessarily see metal flakes but there was alot of sludge at the bottom of the pan and the fluid looked burned / very dark.I changed the conductor plate / filter and plug and refilled the transmission to the proper level .So now I take it on a test drive .The first time driving the vehicle I might add.First thing I notice is no check engine light and I didn't clear any codes.Its not in limp mode at all,but reverse isn't engaging at all . When in drive the shifting is eratic .Im pretty sure the transmission is shot .I'm planning on finding a used working transmission .My question is how interchangeable are the 722 .6 units .As far as car models/years .Does it have to be exact or will it have shifting problems otherwise . Like to say Thank you in advance ,everyone here is always very helpful and I appreciat that .
 

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Check the wiring connector for oil. Also check the TCU for oil intrusion. Also check your radiator to make sure it's not the Valeo that lets coolant and fluid mix:

Benzbits: Valeo vs. Behr Radiator
 

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Thank you. I couldnt find where to add that information .I checked the tcu and it was dry and the adapter plug was dry as well ,but I went ahead and changed it .I was talking to a mechanic today and he thought the problem was isolated to the valve body and that would be the part I needed to replace .Any thoughts on that?
 

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I am no expert ,, but I would say that could be right. It could be a solenoid issue ,,,
Have you done a transmission adaptation reset ?
I would try that ,,also drain and replace some more fluid to get fresher fluid in it ,,
If still no good , unless you want to scan it or test to check for a bad solenoid , just buy a used 722.6 valve body and put it in with the conductor plate and solenoids it has and see what happens ,,,,before you go the step of replacing the whole transmission.
 

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Yes, it could be a valve body issue, too. Without knowing for sure, I like to go for the cheapest, lowest-hanging fruit.
 

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It's an 03 and you found sludge in the oil so check for glycol contamination in the ATF. Swapping out the transmission is going to be a bit of a waste if the radiator is still dumping coolant into the ATF.
 

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If you have the Valeo radiator, then I would replace it and also do a fluid change and flush.
 

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Some say that if the radiator was bad it would have failed long ago. If your car was built after Sept.2003 then it will be good.
Dark sludge and dark fluid is to be expected after 16 years with no fluid changes...dark sludge in the pan comes from worn clutch material.
Trans. fluid with some coolant in it will be lighter in colour ,,,not darker.
If you have not lost any coolant , and if you don't know for a fact that coolant is in the trans fluid , then it could be a waste of effort to change the rad ..
and it will not solve your trans, shifting problems.
 
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