I have a 94' volvo 850glt.I just replace the from brake rotor and pads and everithing is fine, the brake system works great. The problem is that sometimes (not always) the entire body start shaking hard (only a low speed, in high speed nothing happen), It only happen when I press the brakes (decreasing the speed around 10miles per hour until the car stop). the problem happen just a few second, not always do that,and is gone after I release the brakes, after that the car keeps funcionating just fine and the brake system works normal not dragging sounds or pulling to one side occurs. I am thinking about the transmision or suspension because it sound like my car's tires are scraping the chasis or something. I checked the space betwent the tires and chasis but everething seens normal.

Plese answer me what do you think it can be?
Sincerely,
Jorge