Yesterday, when slowing in a parking lot (5-10 MPH), and taking a slight right turn, I got a HUGE vibration in the rear end of the wagon. From the driver's seat, it seemed as if it came from the right side, but I can't swear to it.

This wasn't a "slight" vibration --- and it wasn't "out of round rotor"-type vibration (had an 850, I've had PLENTY of those !!!)..........it literally shook the entire rear portion of the car -- it was that loud. It was also a constant frequency -- that is, it didn't raise or lower in pitch depending on my speed. It remained the same (rather low) pitch the entire time it was going on. As I came to a gentle stop, it (quickly) got softer and stopped.

It definitely seemed to be associated with the braking, somehow. Braking effectiveness was not apparently affected. No pad squealing that I could hear.

What was odd was that when I braked from a FASTER speed, or braked HARDER, the vibration didn't happen, even making the same right hand turn. It only happened when I was already going very slow, and VERY GENTLY braked to a stop.

I started wondering if it was some sort of ABS sensor malfunction --- causing the ABS to activate on one rear brake. The reason I speculate this is that it almost seemed that another "force" rather than my braking force was activating the vibration.

I've never experienced this type of thing in 24 years of Volvos, so any suggestions anybody has would be most welcome.