ON MY 743, WHEN I USE THE PARKING BRAKE IT IS REALLY LOUD AND COMES FROM UNDER THE CAB. WHAT IS CAUSING THIS? DON'T THINK IT SHOULD BE THIS LOUD
What do you mean by loud?
What kind of noise is it making?
The brake works by two pads squeezing a disk that, when the machine has stopped, does not spin. So no noise should be coming from the brake when it is engaged. Unless the machine is trying to move with the brake on, which then the noise could be the relief valve engaging or if the brake pads are worn and the machine moves when the brake is on then the brakes could make noise.
Does your machine creep when the levers are in neutral?