Drive train whine at freeway speeds
10-27-2009, 08:20 PM
#1
Drive train whine at freeway speeds
I have a 2003 C-coupe with auto trans and V6. The drive train and suspension are all stock with the exception of 17" rims. It has 112K miles on it.
About 15,000 miles / 1 year ago it started producing a whine at 71 mph from the rear of the car. It started out very soft, and has gradually gotten louder. It now can be heard at any speed from 68 to 80 mph, and is loudest at about 74 mph. If I go faster than 80, even up to 100+ it is silent.
If I let off on the gas, it immediately becomes silent. So I suspect that it is the drive train somewhere.
I have tried altering the engine speed by driving it in fourth. It does not change. So it is not the engine. ( If it were the engine, it would appear at a lower speed in 4th )
During the past year ( not as an attempt to fix this, FWIW ), I have had the wheels aligned, tires changed, and fuel pump replaced. So it is not any of those.
I took it to the dealer, he diagnosed it as the differential. He replaced the differential. The whine is still there. So it is not the differential. ( He has agreed to refund, BTW )
I suspect that it is some kind of bearing in the drive train, and I wish to find it before it fails catastrophically. Anybody got any idea of what it might be? Thanks.
About 15,000 miles / 1 year ago it started producing a whine at 71 mph from the rear of the car. It started out very soft, and has gradually gotten louder. It now can be heard at any speed from 68 to 80 mph, and is loudest at about 74 mph. If I go faster than 80, even up to 100+ it is silent.
If I let off on the gas, it immediately becomes silent. So I suspect that it is the drive train somewhere.
I have tried altering the engine speed by driving it in fourth. It does not change. So it is not the engine. ( If it were the engine, it would appear at a lower speed in 4th )
During the past year ( not as an attempt to fix this, FWIW ), I have had the wheels aligned, tires changed, and fuel pump replaced. So it is not any of those.
I took it to the dealer, he diagnosed it as the differential. He replaced the differential. The whine is still there. So it is not the differential. ( He has agreed to refund, BTW )
I suspect that it is some kind of bearing in the drive train, and I wish to find it before it fails catastrophically. Anybody got any idea of what it might be? Thanks.
10-27-2009, 09:55 PM
#2
Super Moderator
you were lucky he refunded your dif that is very expensive. i also have a whine/droning from my car but it only happens at i think exactly 40mph but i drove two other older c320's and they both did it so i stopped worrying. gl on your problem i have no clue what it could be.
10-27-2009, 11:16 PM
#3
MBWorld Fanatic!
You seem to be isolating the problem, albeit the hard way 
All that's left now is the drive shaft, u joints (all), transmission mounts & output bearing, rear wheel bearings, and flex discs. You should be able to inspect those items for wear or breakage. samaritrey is right, you're lucky they refunded the cost of the differential, probably the costliest of all the culprits to replace.
All that's left now is the drive shaft, u joints (all), transmission mounts & output bearing, rear wheel bearings, and flex discs. You should be able to inspect those items for wear or breakage. samaritrey is right, you're lucky they refunded the cost of the differential, probably the costliest of all the culprits to replace.
10-28-2009, 06:03 AM
#4
Super Moderator
These cars do set up a slight harmonic at about the speed you talk of. This sounds worse. Check all that mleskovar wisely recommends.
Also check the rear sub frame mounts. Try & borrow a set of wheels from a friend with a different brand of tyre. W203s are sensitive to any tyre with a large block pattern. Can sound just like a failing bearing at some speeds.
Also check the rear sub frame mounts. Try & borrow a set of wheels from a friend with a different brand of tyre. W203s are sensitive to any tyre with a large block pattern. Can sound just like a failing bearing at some speeds.
