The Stovebolt Site Forums The Shop Area Driveline sticking parking brake

Yesterday I took my 53 one ton out for a short drive, just checking things out before I get it inspected next week. Everything went fine driving out my road, but coming back it started straining and loosing power. When I stepped on the clutch the truck came to a quick stop, and when I let the clutch out it shuddered trying to get moving.
I finally decided that the parking brake was somehow engaging, but I managed to coax it back home driving slowly. When I parked it the engine was steaming, and I could smell the rear brakes. Also, I had very little free pedal on the brake pedal, grabbed hard after pushing it in about one inch. And the rear drums were hot. I let it sit overnight, and this morning started to check things out. Jacked up the rear wheel (drivers side) and it turned easily with no grinding or grabbing! I haven't pulled the drum yet, but thing seem to be working normally now.

Any ideas what might have caused this? I still haven't checked the other rear wheel, but I'll do that after I get finished with the driver side. This was a huge disappointment, thought I had it all set!

Tim

Does the MC pushrod have adequate end clearance?

Ed

If this ever happens again, remove the clevis pins from the levers on the parking brake cross bar. This will release the parking brake cables and rule out the parking brake as the issue. While the cables are disconnected, pull on them to see if they will pull out and return as designed.
Then do what Ed says. He is always right. (I have never witnessed him being challenged on his advice.)
Carl

The parking brake cables were loose when I checked them. I pulled them to take out slack and they grabbed, but released when I stopped pulling. So that seems to be working.

I'm wondering if I somehow got the brake shoes installed wrong. Or...I noticed when I did the brakes (many months ago) that there was a small groove worn in the backing plate where the shoes slide. Maybe the shoes are getting hung up on that.

Tomorrow I'l be pulling the drums off both rear wheels, hopefully I'll see something then.

Tim

It is always best to take a picture before disassembly, it might be years before we get to it, or might get distracted by another truck.

Ed

If you pull the parking brake on while on the stands and then release them, the wheels should turn free. Also there should be no drag from the brakes when at rest. Those one Ton drums are very scarce so this is one problem you don't want to linger.

Actually I have a drawing of the rear brakes, from years ago when I first took things apart.

I was talking to a friend who is a former mechanic, and he suggested that it might be a problem in the master cylinder. I told him that along with the other symptoms, I had noticed that the brake pedal only went down about an inch before stopping, and he thought that something might be preventing fluid from returning to the master cylinder. And this is a dual master cylinder, so it might only affect the rear brakes.

Tim

Well, I think I might have found the problem. When I got into the passenger side rear wheel, it wouldn't turn at all. I baked the adjuster all the way out, pulled the drum, and found the front brake shoe out of place. It looked like it had slipped over the top point that it slides on and couldn't come back. I took the shoes off, cleaned everything up well, and put a small amount of lube on all the friction points. After everything was back together it looked good.
I still have to finish adjusting the rear brakes, but on a short run it dd OK.

Tim

Make sure that all of the shoe retracting springs, and center shoe retaining spring and pins are in place. Shoes don't randomly come off.

All the springs are new and in place. The only thing I can think of that I didn't do was adjust the big anchor pin, mostly because I couldn't get the nut to turn to loosen it, but also because I can't figure out how to check the clerance of the shoes with the drum on.
Or maybe I'm very confused about the whole thing.

Tim

The Chevrolet Truck Shop Manual describes the anchor pin adjusting procedure quite well. It is an important detail to perform when replacing brake shoes.