Notfastenough

I'm new here, I just bought a 06 C55. It's got 50K on it. However I got this problem with the transmission, sometimes after a full acceleration in M or S mode, (~40-90mph) the car's transmission would disengage, even though it says it's in D or 5 (cycled M/C/S). It would just rev. I tried switching to N and back to D, and nothing happens. Only after the speed falls below ~40mph, the transmission engages again. Has anyone had a similar problem? or any idea for on why I'm having to issue?

Dingleberry

check fluid level

RW C55

+1, I had the same problem, took in back to the dealer and turned out to be insufficient tanny fluid.

MIKESV8

i have the same exact car and i'm new on here too. it's not a problem with your car, it's meant to do that so that you don't blow the tranny or engine. all you gotta do is take traction control off and your problems are solved. sport mode is also best to have on when you do floor the car.

Phil C55

It depends on if his is really completely disengaged or it is just thinking he still wants to play and it is staying in a lower gear and ready to get it on. The brains in the tranny will stay in play mode (I.E. high revs and a lower gear) for a bit after a hard pass. If you go back to cruising it will shift up after a bit and the revs will come down. It isn't programmed like this so you won't blow up a motor or transmission, a rev limiter protects the motor. No, it's just the adaptive side at work or it may be a problem if it is actually disengaged.

MIKESV8

has it happened to you before phil? i noticed you have the same car. my sisters 02' c240 doesn't do it.

Phil C55

I'm not entirely clear on what you mean has it happened to me before. If you mean being adaptive and staying in play mode after a hard run, then yes it does that every time. My 18 year old son thinks it's the coolest automatic in the world because of it.

Has the transmission ever completely disengaged and acted as if it were in neutral until I slowed down, no, never.

Your sisters C240 won't do it because it doesn't have the AMG Speedshift transmission we have. These are supposed to shift 35% faster, be adaptive which means if the driver is driving it hard, I.E. wide open throttle for so long, then when you slow for a corner it won't upshift and then down shift coming out as you get back on the gas. It will stay in a lower gear through the corner and not be hunting for a gear. All this is done through the mapping of the computer that controls the engine and transmission.

MIKESV8

that does make some sense phil. and tell your son he is absolutely right. i got my c55 a couple months ago while i was still 18 and thought that it was the coolest automatic in the world. i had the factory pirelli p-zero's still on the car when i bought it but those didn't grab traction for crap (they are only 245's in the rear) but i recently purchased michelin ps2's and they are amazing. traction like no other. the $1500 pricetag for the set might set you back a little though.

Quicktwinturbo

Off topic.. I was ride'n in my friends S550 last night and he told me to use S-mode instead of C-mode.. It's a lot better for your tranny to start in 1st instead of 2nd... and one Korean MB mech agreed...

Any mech or members can confirm that? I usually drive my car on M or S so it really doesn't matter but i thought this was interesting.

Dingleberry

why did you mention that he's korean?

also

Quicktwinturbo

Cuz i'm in Korea n he is korean?

Phil C55

On the surface it makes sense, but the car isn't that heavy and the motor has the torque to pull a second gear take off with zero effort or problem, the transmission is made to handle all the power and torque these cars make and then some. I use the S mode only, but used the C mode for a while when I first got the car. I doubt by using the C mode it would reduce the life of the transmission.

Notfastenough

my trans actually disengages, because the rpm drops to idle and when i rev up nothing happens other than my rpm going up. oh yea, the display still reads 5 or D depending the mode i'm in. I also read on other threads (with similar problems) people recommend them to update their trans program or replace their speed sensor, should I do those too? how much do those cost?

Notfastenough

can I check the trans fluid myself or do I have to take it into a MB shop? because from what i understand there isn't a trans fluid dipstick. (from reading other threads)

Phil C55

I would take it to a shop just to have it checked, shouldn't cost hardly anything. If you buy the dipstick you still need to get the transmission fluid up to 80 degrees C to check the level. The dealers diagnostics tell them the temp.