DanC230K

Hello all,

I have a 2010 C250 4MATIC Sport (the 2.5L M272 is a Canadian market exclusive) and I have a potential transmission or some other issue with the car. Mileage is 90,000km and I had the transmission serviced at a reputable MB dealer at the 60,000km mark as is mandatory. Looking back I do not believe they drained the torque converter, however. The service was in the summer of 2011. During the early spring of 2013 I had the transmission fluid level checked when the car was in for an oil change because as most of us know MB decided (stupidly and deliberately) to not include a dipstick. They claimed the fluid level was ok.

What is happening is that after driving the car after about 30 mins and having everything warmed up I hear a sublte whistle/whining from the transmission only when I let off of the gas at only two speed ranges and in any gear – 100 down to 90kph and 60 down to 50 kph. The transmission shifts perfectly and no whistle is heard when the car is cold. The noise only appears after everything is warmed up and disappears once any throttle is given. I have also noticed a burning smell when leaving the vehicle after it has been driven at length at higher speeds.

Someone on here suggested that it may be a front or rear differential issue (or transfer case) as the noise is speed specific and is not tied to RPM’s. However, owning the car for several years now I am quite sure this is a transmission noise.

Quite frankly with all the issues people have had with this abomination of a transmission I am very paranoid about having issues with it. I do not drive the car hard and I carefully warm up all the fluids every time I drive the car before driving with any aggressive throttle whatsoever.

If it was my torque converter going, what would be the signs? Should I do another fluid service and get a sample from the transmission/torque converter to analyze? Will a fluid change make any difference?

In addition, I have had new tires installed recently and the techs had to stretch the two rear 225-45R17 onto the rear 245-45R17 to make them fit. The only way I went along with this was I was assured this would work as the tire can be stretched a couple of inches to accommodate a wider rim. I included this as I have heard this can potentially cause weird noises when the car is coasting.

So, any ideas?

Thank you for your time.

Carsy

Did the noise begin with the tyre change ? . I would find someone to borrow or swap a couple of tyres back to the original size & for a temporary test.The dealer might help.

Putting the car on a hoist should show you if you have an oil leak to the manifold or exhaust. It may be related to the noise.

The way 4matic transmissions are dying it is a fair bet that this is the trouble.https://mbworld.org/forums/c-class-w...ine-sound.html

I have a whine which is rev related & I thought it was the ATM but found it was the A/C when lightly loaded ie in mild weather.

DanC230K

Thanks for your time Carsy. I am thinking about booking it in for the dealer again. I forgot to mention that I just had the service B done a month ago and they said they inspected the driveline and found no issues as I have also been feeling a lack of power and a weird rumble around 2000rpm sometimes. So perhaps I need to explain in more detail what the symptoms are and some more through checks by them may be able to find the issue. So you may just be spot on in regards to the intake of exhaust manifold. I check the engine oil level regularly and I never need to add any so could it be trans fluid leaking somewhere because this would be much harder for me to spot. In addition, I never notice any leaks where I am parked.

I suppose it could be A/C related as the compressor makes an awful noise sometimes. In addition, this all started happening after the temperature dropped here (Edmonton has one of the harshest winters on earth - last week it was -50 Degrees celsius with the windchill). Perhaps these extreme temperatures are another reason for what is happening.

I am also ready to just trade it in on my next car, a 2014 Honda Accord I-4 Coupe in red. Overall, my C-class has been excellent except for a faulty thermostat which stuck open and was fixed under warranty a year ago. If anything I over service the car and if I have a major issue here I will be just livid. The thread you linked to is quite scary and is one of MANY I have read over the past few years regarding the 7G. I should have done more research on these issues before buying this car. I never had any issues with my '03 C230 and even then M271 is one of the worst engines out there as well ha ha. It is sad because when this car works perfectly it drives so very nice but clearly all the testing done was not sufficient...

Oh and yes the noise seemed to start after I had the tires changed.

Carsy

Good luck & let us know the outcome. John

RED E350

Hello DanC230K, Carsy,

did you figure out the whine/whistle noise when letting go off the gas pedal?

I have a 2009 e350 CDI coupe and a few days ago I started hearing a whine/whistle noise when I let go off the gas pedal at 60-50 kph and 100 to 90 kph speeds and only after the car has warmed up, the sound only lasts a very short time, and I do not get it every time. I suspect the 7G transmission.

DanC230K, you posted about harsh winters in Edmonton - was the sound related to the weather at all? I live in Slovakia, and the winters here are mild compared to yours, yet the sound appeared after the temperatures have dropped to -1 to -8 C for a few days and stayed there. Could it be the transmission fluid reacting to the cold, or some other issue?

Or was it the A/C, as Carsy suggested? The whine seems to appear when the transmission shifts upward at around 2,500 - 1,500 rpm in the 60-50 kph and 100-90 kph range, therefore it seems to be rev related, and it started with the low temperatures.

Guys, I am new to the forum, and any help would be greatly appreciated! The frequent occurrence of the 7G failing with these cars is quite a scary topic!