Kar don

Anyone have this? Comes from the rear of the car. It almost sounds like a subwoofer is just holding a really low note when I hit this speed. (2003 C320 4matic). Dealer said it is because I have hard tires (michelin primacy mvx4) but I dont buy it. I tried different rims/tires on the rear and the noise still existed. What do you guys think? There are 57k miles on the car.

mleskovar

I don't have a 4 matic but if you changed the tires/rims (unless they are like the ones you replaced) and the noise remains then to the dealer's 'guess'. Did you tell them you tried different wheels? If it's not related to motor rpm then it must be in the drive train. U joint - flex disc - differential - wheel bearings - etc. Does it make the noise during acceleration, cruising, or slowing down? What speed?

Kar don

yah its def in the drivetrain. I tried accelerating, downshifting, etc still was the same noise. The noise is loudest at like 70mph and pretty much plateaus there. The tires I put on were the Original equipment michelins, same exact noise...actually had more tire noise, I hate dealers try to find any excuse not to do work and charge you a BS diagnostic fee.

I originally tried changing the rims because I thought I possibly had a bent rim, but thats not the case.

mleskovar

How sure are you it's the rear, what makes you think that it is? Have you had your thrust bushings replaced yet?

mleskovar

Does it make the noise constantly while rolling but becomes the loudest at 70mph and 'plateaus' there?

Glyn M Ruck

This is typical of Tyre noise. Run your hand over the tread counter to rotation & see if you can feel any feathering, lipping or cupping. I'm afraid it is fairly typical on these cars. Michelin Pilot Exalto PE2, new PS2 with Exalto non directional tread & Yokohama AVS db2 are known to cure this. Stay away from Continental SCs

You should fit non directional tyres and rotate them corner to corner every 10,000 Kms to change their direction of rotation & all will stay silent.

It might be something else but that drone that does not change with positive or trailing throttle or what gear you are in is typical of tyres. Had hell on my car with Continental SC2s. Removed at 10,000 miles and fitted Exalto PE2s - no more drone & wheel bearing like noises.

Kar don

I am using all season tires, this is not tire noise. The car did this before new tires and I thought it was the tires so I replaced them. The noise continues even with the new tires. Michelin Primacy MXV4 are some of the highest rated quietest tires on the market.

What makes me so sure it is coming from the rear? I guess I can't say for sure but I feel the noise more in the floor boards than the steering wheel and it sounds like to me it is in the rear. I read some threads about rear diffs going bad and it sounds like the same symptoms as that.

Also by the noise "plateau'ing" I mean it gets loudest at 70mph and doesnt really get louder when I go up to 80mph... but then again I don't drive over 70 very often . That's what the CLS550 is for

Glyn M Ruck

If the pinion bearings in the diff have lost preload the noise should change from positive to trailing throttle. So your diagnosis is a carrier bearing failing?

What Mileage on the new tyres? I'm well aware that the Michelins are quiet tyres.

Kar don

Mileage on the new tires is about 10k... did it since 0 miles on the new tires and prior to the new tires.

Glyn M Ruck

OK - then it's unlikely tyres if it did it from day one on the new set. I'm afraid it's down to a process of elimination then. Everything from the transfer case back including exhaust & exhaust hangers. Keep us in the picture. Also check the fuel pump under the back seat for noise. One mans drone is another mans buzz. The trouble is that these cars have a natural harmonic in the speed range you describe & this seems to amplify noises.

C230 Sport Coup

I've been having something like this lately.

I've pulled over several times thinking I have a flat...then, I check all the tires ...nothing. Wierd.
When I get back on the road, it seems to be gone.

All I can think, is that I'm running soft compound tires, and the temps have gotten very cold lately. The times it made the sound, I had hit some rough
areas of pavement.

I don't know if this helps, but it does seem that summer tires, when they get very cold they get hard, which results in more road noise on rough pavement.

Kar don

Well the car is at the dealer now. Lead tech drove the car with me, felt the trans delayed upshift (studder) 2 to 3 and immediately heard the noise. Very well described it as driving on the highway rumble strips. He doesn't think it is the rear diff but thinks it is the Torque convertor/transmission. He feels the clutch components in the T/C were damaged by the glycol, we'll see what they come up with!

Glyn M Ruck

Interesting - Lock up convertor clutches. So your car has seen a Valeo radiator/cooler failure? You did not give us much history.

Keep us posted

Kar don

Haha sorry, I should have printed the VMI for you. Also it was built in that lousy Bremen plant

Seriously though, had the valeo radiator issue. Was done about 11 months ago, dealer only did a trans flush, change filter, change radiator. This technician seemed pretty good, waiting on their phone call!

Glyn M Ruck

Good luck - at least it sounds as if you are making progress.

Kar don

UPDATE: Per MBUSA instruction they could only flush the transmission and replace the Trans control unit. They will install it monday and retest for the noise. The tech thinks they will have to replace the T/C or trans but unfortunately he has to listen to MBUSA as they are paying for the repairs.

Glyn M Ruck

Look on the bright side - you'll have a nice new TCU with your new transmission.

Kar don

haha I wish it was a new unit, it will probably be a remanufactured unit

ChrisBrown

Glyn, sound like our conversation all over again, except for a different noise.

You're right this car has it's own set of "sounds."

Glyn M Ruck

Chris, yes, indeed similar. We all want to help fellow members but describing noises to someone halfway round the world is not easy. I had this idea of a glossary of sounds and explanations - but soon realised it was a daunting task. We're all supposed to be English speaking but use different language. Imagine trying to make sense to someone in Malaysia, Singapore, Philippines or Brasil.

mleskovar

To the best of my knowledge MB only uses new replacement parts.

Glyn M Ruck

In South Africa it is policy to only use new parts.

Kar don

Update: New TCU and trans fluid didn't cure the problem. They have now ordered a new valve body and seem to think that will cure it. If not that then they will replace the torque convertor.

Glyn M Ruck

As you predicted Valve body might do the trick??? but it tells me they have not diagnosed the problem

mleskovar