Loud noise in Buick Rendezvous

I have a 2005 Buick Rendezvous AWD and it makes a lound humming noise. The noise seems to be coming from the back of the vehicle, underneath the third row seats. It gets worse the faster I go. It does not matter if the RPMs are high though. I can be going slowly up a steep hill and get high RPMs and the noise is not there. It is worse when I am travelling at 55-70 mph. I have taken it to the dealership and they don’t know what it is. My local mechainc said Rendezvous are just loud. Any ideas out there?

This sound could be from a differential that is going dry. Have a mechanic check the rear differential to verify that it has sufficient lube oil remaining.

I suggest a different mechanic than the local one that you used previously. If that mechanic did not check the diff when given this description of symptoms, then he is…not very interested in finding the problem, IMHO. And, his statement about that model just being loud is not very reassuring.

If the differential proves to have sufficient lube oil, then I would suggest having the tires rotated to localize a possible tire problem. Many tires tend to get noisy when the tread has worn a bit, and it is possible that tread wear—or a tire defect–is causing this noise.

In addition to checking the rear differential oil, I’d also have the rear tires closely inspected. An unevenly worn tire, or a tire that is nearly worn out, can make a lot of road noise at speed.