Rear Brakes Dragging

[charrisboyette]

Hey Guys,

I’ve got a GMC 63 half ton that is stock. Had it for a few years now. Took it to a shop a couple of years ago because I was having a hard time stopping. They replaced the front right shoes and wheel cylinder. At that time my pedal got hard but it stopped really good. I thought that was how it was supposed to be as I had never had non-power brakes.

Fast forward a couple of years and I have been chasing down an overheating issue. I checked the wheel temp after a hot drive and the back brakes were very hot. The fronts were not even warm. Identified that problem hopefully. I wrestled the drums off and replaced the shoes, wheel cylinder and drums for both brakes. I also checked the adjustment of the hand brake cable. The rears are still dragging.

So, is there a difference in the two wheel cylinders? I see that there are two available. I ordered both but replaced them with what was there. Could the wrong ones cause the issue? I have the star adjusters completely adjusted in. I am at whits end. Was I supposed to use GMC specific brake shoes that they don’t make any more? I’m starting to humor deleting the hand brake as a possible solution but wanted to hear something sane since I am well aware of the dangers of getting rid of that on a single channel brake system.

Sorry for the novel. I was just trying to put as much info out there as possible. Any ideas would be greatly appreciated. I actually use and enjoy this truck.

[James]

When you installed the rear drum did they slide on easy? Do you have slack in the parking brake cable? With the rear wheels off the ground, you should have been able to turn the wheel easily from either side. Was the width of the old shoes the same as the new ones? Was the drums the same dimension?

Pull off the drum and inspect the side (the side/edge that is next to the drum) of the shoe. If the side of the shoes show wear, the shoes (too wide) or the drums (too narrow) is wrong.

Also can you provide a pictures of the brake assembly (with the drum removed)?

[ilvracn]

Do you possibly have the rear shoes on backwards? Shoe with longer friction material usually goes to the rear.

[James]

Originally Posted by ilvracn

Do you possibly have the rear shoes on backwards? Shoe with longer friction material usually goes to the rear.

You are correct, the longer shoe goes on the rear. However being installed backward would not cause his problem.

[charrisboyette]

I have the large shoes to the rear. As far as wear on the old ones, they were pretty obliterated by the heat and my attempts at getting the drums off. The shoe backing appears to be the same width but doesn’t mean they weren’t too big before. The parking brake cable has slack in it. As far as the drums go, they were supplied by Rock Auto so I hope they are correct. They fit otherwise. The wheels do spin freely side to side with just a slight noise. The drag does increase when the sun heats everything up. I’ll get the tires off in a couple of days and get some pics.

[ilvracn]

is there a lip on the drum that the shoes are dragging on? wheel cylinders sticking? arm for park brake on backwards? wrong return springs?

[charrisboyette]

The drum has no lip as it is new. I also replaced the wheel cylinders. The return springs were replaced with two grey ones per side. I put the parking brake arm back on the same way it came off. It does match what it looks like in the repair manual.

[LEWISMATKIN]

more than likely the rear flexible line has a flap in it or has collapsed partially. this would cause the brakes to drag, because the springs can't pull the wheel cylinder completely collapsed. to verify, once the problem occures, loosen one of the bleeder screws on one of the wheel cylinders and if the brakes release, replace the rubber line at the top of the rear axle. due to the age of the truck, I would replace all of the hoses at this time.

[charrisboyette]

That is one thing I hadn’t considered. I even put stronger springs in to no avail. If I use the hand brake, the only way to get the shoes back is to bleed it. Thanks for the insight. I will most definitely do it.


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