2001 C240 feels like it upshifts (or torque converter unlocks) when slightly
accelerating during normal driving. Occurs in 4th and especially 5th. No slippage and more agressive throttle input just causes the expected downshift..but subtle accel and it feels like it falls out of lock-up..ideas, experiences anyone?

 

Have you changed the sauce? I changed mine at 110,000 miles. Complete flush using a pump, not just a remove the pan and drain. I was sensing minor shifting problems and the same feeling of the drive train not quite solid on accel.

It is like driving a brand new transmission now. I should have changed it earlier. The sealed for life or 150,000 miles must have been engineered by the marketing department. The rest of the world has much shorter replacement intervals.

 

lol about the marketing department! The year prior to mine has the same trans, filter, and uses the same fluid and the book says service at 60k... Yes, mine was serviced about 10k miles ago. This problem is very recent as far as I can tell. My wife usually drives it but lately we've been commuting together and will trade driving spots each day twice. I'm hoping it's just an adaptation issue..confused car.

 

Check trans fluid level and if it's low check the trans plug for leaking.

 

Thank you, I will do that.

 

Fluid is full, no leaks. Anyone else experience this symptom?

 

The TCU for 2001 is different to later models & can't have software easily reflashed or I would recommend this. Please check that the TCU bush (plug) into the RHS front diagonal corner of tranny is not suffering the dreaded O ring leak. Oil wicks up the harness & gets into the TCU under the passenger foot plate (inside cabin under carpet).

 

Thank you, I will check for this leak when I change the engine oil.

 

No leak except some rear main seapage wich seems to be pretty common. The symptom hasnt occured very much in the last week..maybe it reprogrammed itself? lol

 

It might just be TCU "brain fart"

 

I need to get it to a dealer to get it updated or somthing. It has straightened out latey so your are probably correct. stupid computers.