You didn't say much about the symptoms of your problem, but if by "extra sensitive" you mean the rear brakes lock up very easily, I had the same problem on a toyota pickup. In my case, the differential had been overfilled with gear oil, which made its way through the axle tube into the brake drum. For whatever reason, that oil made the brakes so grabby it was an unbelieveable hazard. All I had to do was change the brake pads and check to make sure the oil was at the appropriate level and that solved it.
