Last week I started to hear a noise from under the car. The sound was a high pitch metal-to-metal squealing noise and was speed based not RPM. My initial thoughts were that it was a wheel bearing or drive shaft problem. I ruled the wheel bearing out by doing some quick turns back and forth and taking the load of each bearing to see if the sound disappeared. It didn't, so I ended up taking it into the dealer on Saturday.

The lead mechanic went for a test drive with me and initially though it was also a drive shaft issue. He said that he had another W204 come in recently that was making the same noise. The noise was due to the heat-shield material (a felt like material) coming loose and hitting the drive shaft. Said it was a 15min fix if that was the problem. He also stated that this was a common thing he has seen on the w203, but the not on the w204 yet.

They put the car on the lift and after a half hour they came back and said thats not the problem. So we rescheduled for this morning so they could look into it further and so I would have a loaner vehicle.

Anyways, they just called me a little bit ago and it appear that the transmission had failed. I didn't get a lot of details from the service writer, but he said they will have to replace the tranny. The good thing is that it is covered under warranty. I'll get more deals but he said two component inside the tranny ceased together. The weird thing is that the car ran perfectly fine.

I caught this issue right before my regular warranty was up so I though I'd post it incase someone else was having the same issue. I think this case is pretty rare/extreme but a new transmission not under warranty can cost you a fortune, so if you hear/see the same symptoms, I'd have the dealer check it out.

Here's some info of the symptons. I'll post more about the exact cause of the issue when I find out more later.

Model: 2008 C300 4MATIC
Transmission: 7G TRONIC 722.9
Miles: 47,000 miles
Symptons: High Pitch Metal-to-Metal Squeal from under the vehicle. Sounds is speed based, not RPM and is constant. The noise is only noticeable with the window UP and music off.

 

Wow,
You got in just under the warentee? That's great news. Just for reference see if you can find out what the price would have been if you had to pay for it. You are getting a brand new one, not a refirbished one right?
Kind regards,
Rick

 

Did you have the transmission fluid changed at 40K miles?

 

Luckily under warranty. This can't be cheap. I'd be screaming and hollering (ina very nice way) for new parts.

 

Do the c350 and c300 share the same tranny?

 

Sounds like the Torque Converter, input shaft bearings, oil pump failure.

See here:

https://mbworld.org/forums/c-class-w...ghlight=gentle

See attached thread "I may have broken something" for audio clip.

 

My 2010 c350 4 matic recently developed a whining noise. Not too loud but audible when radio is turned off and windows are shut. It is almost like a turbine whine that increases in pitch as the speed increases. The whine starts at 60 KPH. It is most noticeable when driving at constant speed and when decelerating. Just to be sure that the whine was not coming from the engine, I've listened to the engine while the car was stopped with an open hood. I've increased the revs to simulate normal engine speed when driving and the whine was absent. Next, I drove the car and when the whine appeared I shifted to neutral just to eliminate the engine as a possible source of the sound. I found out that the whine was still there and that it was dependent on speed (I.e. as the car was decelerating, the whine was going down in pitch). It must be coming from the drivetrain then. Could this be a symptom of an impending transmission failure? I've Followed the thread here and it seems to point in that direction. Thanks.

 

Post a clip!

 

I have noticed a similar thing but it's more of a humm rather than a whine...dont know if it some kind of ball bearing issue.

 

Or sooner?
Are you getting a new transmission?
Will you be buying an extended warranty that covers the transmission?
Many 722.9 owners want to know.

Wayne

 

Sounds like your differential could be bad. Is the car under warranty? Go back with it ASAP.

 

My GLK 350 has the 722.9 transmission. I'm sure your C 350 does as well. The 722.9 is used throughout the M-B line.
I wish TheDarkSide would return and fill in some missing information. A "hit & run" post leaves many questions unanswered.

Wayne

 

guys, i'm going to post here since the GLK forum's too quiet but since my B sevice (30,000kms), i have a humming coming from the front of the car most noticeable when coasting from 60 to 50km/h. During the B sevice, they replaced a gasket from the front transfer case output shaft because the said there was a small leak. My SA said it's my tires as they were rotated during the B service but I've told them i'll be bringing it in Fri for them to rotate the tires back to see if that's the issue. Will keep you guy updated. The noise is super annoying and i've had more problems with my GLK in 2 years than my previouse 2 cars in 8 years combined, lol

 

i have had my Tc output shaft seal replaced twice and the front differential input shaft seal once. I dont know if this is the sign for a imminent transmission failure? My warranty is expiring in about 3 months - should i get it checked again or just buy and extended warranty for about $2.5K.

 

IMHO, any respectable company would "goodwill" any future repaires related to your TC as a result of all the issues. This is my only MB but other makes i've owned were really good at standing behind their products if you run into issues past the warrenty period. I wouldn't get the extended warrenty just got the TC issue....

 

Interesting....The other day, it was very warm, I was driving from early morning, coolish went for breakfast at around 11:00, parked car and ate.

When I pulled away I heard a noise, my 1st thoughts were Oh hell, gearbox. As I get to speed the noise went away, say 1KM, and stay away while travelling and through stop-starts. The afternoon I parked the car again, cup of coffie, as I pulled away same noise, same things.

Only that night in bed, it strike me it could be the front engine fan running at full speed because car was parked. I always look at temp gauge and remember seeing it just a tiny bit higher than usual when noise was heard.Usually I left the car after parked longer unattended.

I left it at that seeing my symptoms. Hope I am not wrong.

 

I just assume that the 60,000KM one-time transmission service is meant to flush the metal debris, etc. I would imagine that not all parts are as clean to begin with as MB has hoped and if a few pieces got to the wrong places before the service and the normal service procedures aren't sufficient to remove them...something like this happens?

Not sure if it's related, I have had to deal with a higher-pitched whistle-like noise at ~70 KM/h when letting off the gas pedal for almost three years since the ODO: 28km mark! From reading the posts here, some suspected/confirmed that it was from the transmission. I was hoping to wait till the transmission service which I'm currently 7K away from to mention the problem. However, the whistle disappeared all of a sudden after service A2 last week. They did reprogram the transmission control during the service, but I doubt that had anything to do with it. I have tried to listen for other types of noises in the event that the original problem has progressed into a worse form, but so far so good.

 

The one time fluid & filter service is nonsense. Service every 60K Km's or 39K miles.

 

Folks , my issue was thankfully the tires. got them rotated back this morning and all is well. Good luck!!

 

Just nticed a light noise on sunday, by tuesday it was more of a grinding noise. dealer picked up with a flatbed.......transmission and transfer case need to be replaced. Didnt get the details of exactly what it was but car has 30000 miles its a 2009 C300 4matic sport. Luckily we are still under the 4 yr 40k mile warranty

My concern is warranty after the repair. I thought all dealers, all vehicles must provide a 12 month 12,000 mile guarantee on any service or repair work wether its covered under general warranty or not?

 

I noticed a wine (almost like a supercharger wine) coming from my cars front the other day when I was cruising at 60mph, sped up mouse went away, back to 60 and the noise cane back on. I could swear it came from the left side of the front, but that could be cause that's the drivers side. I got this new wheels 3 weeks ago, hope it's just the wheels, as the gear box seems to be shifting just fine!

 

^ Same whine around 60 mph as mentioned two-three times in this thread so far.

Loud enough to hear with the windows UP and music OFF.

Seems more obvious when I lift off the throttle around 60 mph.

 

Thats how it started, it was just a whine... I was thinking maybe a belt or wheel bearing. The whine was on Saturday by Monday it was a lound noise and the car was towed. If you have warranty left GET THE CAR IN ASAP!!!


Not sure how long this is going to take for my repair. Anyone have answers on warranty after the repair??

 

Back in March I posted my observations about a suspected whining sound coming from the drivetrain. I brought the car to the dealer at the end of March for further investigation. The technicians worked on it the whole day but could not find the problem. They blamed the noise on the OE Pirelli Pzero Nero tires and I ended up paying $463 for diagnostics since the tires are not covered under warranty (I was told). I argued and protested to no avail. The whining noise was still there (I could distinguish what a tire noise is from a whining metal to metal noise how subtle it may be). Anyway I bided my time and used the car knowing that I had a problem. The noise got worse and louder; the trannny though still shifted smoothly without any problems. On July 23, 2012 I took the car in for "A1 service" and again complained about the whining sound and insisted that I go for a test drive with the technician to ensure that the whining noise is identified. After a short drive the noise was confirmed and acknowledged and upon further examination it was concluded that the transmission needed to be replaced. It was replaced and afterwards I again argued that I was unfairly charged $463 for diagnostics as it should have been covered by the warranty (car was 42000 KM and 2.5 yrs old at that time). After a lenghty discussion with the previous Service Advisor who charged that fee and getting nowhere, I asked him who to contact at MB Canada. He then told me to take baby steps and suggested that this issue will be looked at by the dealership. On July 30, 2012 I got a phone call from the other Service Advisor (who confirmed the whining noise and got the tranny replaced) and was advised that I will be refunded the $463. Just wanted to share; I am now satisifed that the issue has been resolved and that the car is working and sounding properly as it should. For crying out loud this is a mercedes after all. I have owned 6 other cars before (2 VW's, 1 Toyota, 2 Hondas, 1 Mazad) and neither of them had drivetrain issues. The 2010 C350 4matic had 48900 KM when the transmission was replaced. Cheers!

 

I was told that some of the C class cars ( and perhaps others) use a coolant radiator integrated with the transmission cooler. That is, they are basically one assembly separated by an aluminum/plastic (?) barrier. Obviously the lines in and out are separate. however, due to a manufacturing defect in some of these "radiators" the barrier corrodes and allows engine coolant to seep into the transmission fluid. This mixture causes the transmission to fail.

I do not have the details on the exact models, years affected nor do i recall the details of how the compromised tranny fluid causes transmissions to fail. However, i do trust the tech who told me this and MB is aware of the issue.

Perhaps Glyn or someone else could explain this failure mode? Would there be a TSB on this?