2003 Oldsmobile Silhouette Buzzing

DRROCCO

MEMBER
2003 OLDSMOBILE SILHOUETTE
3.4L
V6
AWD
AUTOMATIC
140,000 MILES

At speeds over about 10 MPH, this sound begins in the rear of the vehicle. The buzzing increases frequency with speed. Speed seems to be the only thing that affects it. Acceleration, braking, turning, even coasting in neutral, all have no effect on the noise. I had the wife drive me around the block while I rode in the back and pressed my ear to the floorboard. I couldn't tell if the sound was coming from one side or the other, or both. I put the rear of the van up on jacks this morning, took the back tires off and inspected a bit. I didn't notice any visible problems with the wheels or drivetrain components. I spun both wheels by hand and they felt normal, with no out of the ordinary sound or resistance. That being said, I don't have much automotive experience. I do my own oil changes and brakes and am comfortable swapping alternators, water pumps, changing belts and hoses, etc. Past that simple stuff, I'm in over my head. What should I be looking for in this instance? Thanks!

4 Replies

HMAC300

MECHANIC
48,601 POSTS

Go under the car and bang the muffler with a rubber mallet or your hand/block of wood with a hammer. If it rattles that may be the sound. Also check for shields hitting the exhaust system.

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Tuesday, August 19th, 2014 AT 12:41 PM

DRROCCO

MEMBER
3 POSTS

I didn't see anything rubbing. That was actually my first move. I got underneath and tied back or re-routed anything that could even possibly be making contact with the drivetrain. Exhaust is solid too. Whatever it is can be felt as a vibration throughout the whole van. I'm concerned that there may be something wrong with the rear transfer case or differential or whatever that's called in an AWD vehicle. Is there any way to either confirm or rule that out? Thanks again!