when driving the brakes go smoothly, within mins, they become hard to push,and we end up in a jerking motion to stop the car.
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1998 GMC 1500 Pickup Question: brakes slowly go down ,and becomes hard to push .
Answer #1patrick mannion from Greg Solow's Engine Room, October 15, 2010, 10:24Master
Not sure about the specifics of the braking system on your GMC but a brake pedal that seems to become "harder" to press, more pedal effort required to stop the vehicle sounds like a brake booster that is failing.