DRONING ON AND ON
I have a 2007 Chevy 2500HD that is producing a drone/vibration that can be heard and felt. All this seems to worsen at freeway speeds. I have installed new motor mounts and a transmission mount with no change. It sounds like a diesel with a straight pipe on it. This truck has accumulated 50,000 miles and is all stock.
I checked the exhaust system and found no part of it touching a chassis or powertrain component. I can feel the vibration in the front tires, the exhaust system and the body, but when I touch the frame rail it’s a very light vibration. The drone seems to be coming from high on the engine and is more pronounced at the top of the shift points. I can also feel the vibration in the air filter box. Has anyone experienced anything like this?
Mike Mog Via Email
Duramax’s have drone issues with many aftermarket exhausts. The noise usually happens at a certain fixed RPM and the fix often means a new exhaust system must be installed. However, if you’re certain it’s not the exhaust, have you eliminated the front wheel bearings as a possible cause of the droning sound?
Through the years that I’ve owned diesel pickups I’ve had two that nearly drove me to the brink due to a hard-to-diagnose droning sound. The drone seemed to be related to engine speed, which caused me to believe the annoyance was related to the engine. In both cases, a bad front wheel bearing was eventually discovered to be the root cause of the annoying sound.
What finally shed some light on the wheel bearing issue in one case was that I noticed the sound would nearly disappear when in a gradual right hand curve at freeway speeds. The right side of the truck would unload ever so slightly in the turn, taking pressure off the right-side wheel bearing. The right front wheel bearing had apparently been affected by an 18-inchdeep water crossing I had driven in a few months before. Water must have seeped into the wheel bearing assembly and pitted the surfaces. Why the sounds seemed to be related to engine speed remains a
mystery, though some have suggested that the noise produced by the bad bearing was resonating with the engine and cab structure, which produced harmonics at various speeds. Sounds complicated, but I do know the annoying sounds completely disappeared after changing the pitted wheel bearing assembly.
I replaced the front wheel bearing hub assemblies in my 2001 GMC a couple of years ago for largely the same reason.
The bearing in one hub assembly was bad enough to create a “fairy dust” of steel particles that accumulated on the A-arm and brake rotor. Also, there was movement in the front wheel/tire when it was lifted off the ground. The source of the drone was obvious at that point. Genuine OE replacement Timken brand hub bearing assemblies were available from Amazon with free shipping for about $140 each at that time.