WHILE IN MOTION THE BRAKE PEDAL GOES HARD AND IS DIFFICULT TO STOP. I BELIEVE THIS IS THE CAUSE OF A LOW SPEED INCIDENT I HAD EARLIER THIS YEAR. THE ISSUE OCCURRES MOSTLY AT SLOW SPEEDS IN STOP AND GO TRAFFIC. IF FEELS LIKE THE BRAKE BOOSTER FAILS AND THE PEDAL IS BOTTOMED OUT. IT HAPPENS FREQUESNTLY WHILE HAULING A TRAILER IN REVERSE. VERY DANGEROUS SITUATION.