71 disc drum brakes issue need help
 

I have a 71 Chevy Longhorn with power Disc and drums with with all original equipt. I am having trouble finding my problem. every time I stop the rear brakes lock up under normal pedal pressure. I can stop the truck if I ease down on the pedal but if I hit the pedal normally it always locks the rear. The booster has been tested as well as the master cylinder and the front calipers too and rear wheel cylinders and all lines. NEED HELP> Thanks Critterman71

Re: 71 disc drum brakes issue need help
 

do you have a proportioning valve?

Re: 71 disc drum brakes issue need help
 

If you haven't already pull the rear drums and check for a seal leaking differential grease or a cylinder leaking brake fluid on the shoes.. Roger

Re: 71 disc drum brakes issue need help
 

Thanks for the direction but I have check that also cylinders are excellent and no seal leaks thats why this is so baffling to me. I am now wondering about the prop valve but I am unsure how to test it for my issue, and or if it can be adjusted. Thanks so much for your reply. Keep truckn.