ChesapeakeLimo

Guru's,

re: 2010 W221 S550 4-Matic...

I noticed a muffeled "buzzing" noise coming from the front of the car:

• noise on occurs on deceleration, mainly when letting of the gas from around 65-70 MPH. Fades away below 60 MPH or acceleration.
• likewise, is noticeable when cruise is set in mid-60 MPH and going down a hill. Fades on acceleration.
• appears not to be engine/RPM-related. When the noise occurs I've moved transmission to neutral and it does not impact the sound. Likewise, I've down-shifted when the noise occurs and it does not appear to affect this noise.
• appears not to be tire noise related. Recent new tires.
• seemed to not start occurring until after the car was warmed-up and driven several miles. I did not note the noise after I started the car this morning on the highway until I had traveled about 10-miles +/-.
• if I had to guess, I'd say it appears to be coming from the left front area of the car. If it's of any relevance, I just had the alternator replaced (which is located in that area.)
• I've previously replaced the LEFT front wheel bearing. This sound is NOT similar to the sound that the bearing was making when it was going bad.

IDEAS?

Mike5215

Yeah I'd have guessed bearing too, especially if it's audible on deacceleration and goes away when you hit the gas. The rear diff bearings also do that, although it's more a muffled whine than a muffled buzzing. Can you get it to MB or an Indie and let a tech drive it? They're usually pretty good at hunting that stuff down.

ChesapeakeLimo

Noise was of two things (that I had repaired).

1. The bearing from the front differential that supports the shaft that runs through the donut-hole in the oil pan to the left front wheel (4matic), or;

2. The transmission output bearing for the front drive (which supports the front propeller shaft).

If you experience this have them check both carefully, and pray it's the earlier, NOT the latter. If the front drive output bearing goes it's a transmission as the bearing is NOT available from Mercedes-Benz, no one makes an aftermarket replacement, and Mercedes-Benz states that the bearing is NOT serviceable. So you'd have to replacement the transmission. If you do find yourself in the latter situation, thank the dealer and pay him his diagnostic fee and find a good independent Mercedes-Benz specialty shop to do the labor on swapping the transmission, and order a replacement from Silver Star Transmission in Edmond, OK. They rebuild EVERYTHING and include a torque converter and a new MB valve body, and their warranty is much better than a re-manufactured unit from Mercedes-Benz.