I'm having an occasional severe vibration with my 2001 V70 T5 with DSTC. The milage is 1000 km (650 mi). When the vibration occurs, it can be felt in the entire car, not just in the steering wheel. When it first occurred at about 450 km (280 mi), the sensation was so severe, the chattering from whatever was causing the problem, was audible in the car and the entire car shuddered quite severely.

The vibration has a higher frequency than what one would expect from a problem with a tire/wheel/disk rotor/etc. It's frequency increases as the car speeds up. The higher the speed, the more noticeable the problem becomes. When it does occur, I can feel the vibration slowly increasing in frequency as I speed up until it becomes quite noticeable in the entire car. When I pull on the hand/emergency brake handle just enough to start to feel the car starting to slow down, there is a "clunk" sensation in the hand/emergency brake handle and the vibration ceases.

My dealer as examined the rear brakes, both the disk and drum/emergency brakes. They backed off the adjustment on the hand/emergency brake shoes as they were dragging slightly. This did not alleviate the vibration problem.

Currently, I have Volvo supplied (not dealer supplied) Gislavid Frost II snow tires (215/55 x 16) on Volvo steel wheels mounted on the car. They have been re-balanced and re-torqued when they were re-installed.

Any ideas?