bluedurama

New to my 2008 GX470. 100k miles. Love it so far. However I think I am hearing a intermittent rumbling as I drive down the road. It is like the rumble from a radio base sound. It could be normal road noise but I bet it is not. I have searched many threads on the forum getting educated on these cars, but have not seen anything about this.

I have replaced the left front axle (grease boot broken), replaced the rotors and pads, replaced all differential and transfer case fluids (not transmission yet) and inspected all the suspension parts.

Any ideas appreciated.

chiph9

The driveshaft clunk is heard when you come to a stop and the suspension travel compresses the drive shafts. When you let off the brakes, the tension releases and you'll hear the clunk. You don't hear anything when actually driving.

If the noise changes with your speed, but not with the engine rpms, my guess would be that you've got a wheel bearing going out.

Check with your dealer - some of them have an electronic mechanic's microphone that they can put on the source of suspected noise (sticks via magnets) and record the sounds to help them locate the trouble.

Chip H.

chitown40

I agree that a wheel bearing may very likely be the cause of your noise. Also consider your tires, as tires that are wearing poorly or unevenly, especially as the tread wears low, can cause similar noises.

bluedurama

The noise is like an exhaust pipe slightly bumping something like the rear bumper, or just like the base sound if the radio is slightly off the station and makes a low static. The tires are almost new Firestone and are wearing well. The front bearings seemed good when I checked while doing the brakes. Will keep looking for something loose or slightly out of place. Thanks for the ideas.

chitown40

Ahh, why didn't you say that before?

Look under the catalytic converter. There are thin flimsy heat shields that attach on the underside of the body that tear apart after so many years. They often break and then rest on the exhaust pipe. There are a few of them so check fore and aft along the path of the exhaust. And of course, check the exhaust pipes themselves. The factory ones have a tendency to break right behind the muffler at the weld before it goes over the rear axle.

bluedurama

I'll check that out today. What is the round thing bolted to the exhaust near the rear of the exhaust? It appears to be a counter weight or something.

chiph9

It's a vibration dampener.

Chip H.

bluedurama

Checked out the tinfoil shields between floorboard and exhaust. Looks good except a place it was slightly touching the floorboard. Straightened it out. Test drive, rumble still there. I am wondering if the shocks could rumble when going over uneven pavement. Original, no leaks, rubber looks good. How about the air springs, could them make a noise if something was wrong?

chiph9

No. If the air bags go out, the rear of the vehicle will sit on the bump stops and you'll easily notice how it's riding low. They're either working, or leaking. Nothing inbetween.

Chip H.