2008 4WD - humming noise at high speeds

[glacious]

I just picked up a 2008 highlander sport, ~ 32k miles, 4WD. I noticed there is a low humming noise coming from the middle (or perhaps a bit further back) of the vehicle.

The loudness is directly proportional to the speed. It does not matter if I'm on the gas, braking, or coasting. It almost sounds like an older truck in 4WD where the transfer case made a noticeable hum. It gets pretty loud past at 45+mph, at 70 it's very constant.

Has anyone else noticed this? Is the highlander just loud because of the full time AWD/4WD? Could it just be the normal sound of the transfer case?

Thanks for any insight!

[rupert08]

Mine is very quiet at all speeds. My guess would be the tires is causing the noise. You could try rotating them and see if that makes a difference. What kind of tire are on it?

[glacious]

The tires are Bridgestone Dueler H/L 400 - 245/55R19 (on the 19" Sport rims).

When I purchased it, the test drive showed a slight vibration at 50+mph, so I had them balance the tires, and the vibration is gone... then I purchased it. I don't think I noticed the humming noise before the tires were balanced.

I also noticed that when I swerve slightly at higher speeds (just testing on a clear highway), the humming noise changes or goes away mostly, which I can see coinciding with your tire suggestion.



Now to just figure out what that whistling noise is from the engine compartment @ 2300 RPM (seems like there is a sizable thread on this forum already about it).

Thanks for the reply!

[glacious]

Yup, sat in the 3rd row and let someone else drive today on the highway. I definitely heard the sound coming from the left rear wheel, and the tire also seems to have a more aggressive wear pattern on the outside edge. I'll call the dealer I got it from. It sort of threw me off since it was such a low humming noise. Usually I hear a higher pitched hum when it involves tires.

Thanks again for the suggestion.

[rupert08]

I have the same tires and rims and mine is very quiet. I would still try rotating the tires and the noise could potentially go away. I had the exact same problem with my Jeep a couple years ago and thought a front bearing was going bad. We simply rotated the tires and the sound went away completely and then I eventually ended up having to buy new tires. I bet you will need new tires in about 10K miles, maybe less. You may want them before winter if you have to drive in the snow because they are fair to poor in snow brand new. Good luck!