the park brake pedal assy is self adjusting. the cable out side the vehicle must be slack and if its adjusted that the threads showing are not about 50% you will kill the internal pedal self adjusting feature. I spent a great amount of time studying this flawed park brake design .

Chevy GMC Truck Parking Brake Lever Pedal ResetThis is what you need to do to Reset the automatic ratching pedal that is inside the car. On this one the cabl...

Normally, this *should* adjust itself with the normal use of the parking brake. Most are designed to automatically self-adjust to push-out as the shoes wear down. Much more common on vehicles with rear drum brakes and not "drum-in-hat". But it'll get all junked up with brake dust and eventually not adjust anymore. _____

Repeat Steps 1 and 2 three times to successfully adjust your GMC Sierra's parking brakes. Adjust the Parking Brake. Raise the rear end of your vehicle by placing it on a jack stand and then moving jacks underneath. Locate the steel threaded cables coming out of each wheel well. These connect to an adjuster nut to form one cable. Move the ...