breaks lock up

[turner15]

So my right rear break locks up with the slightest pressure on the pedal.

Its an 80 gmc 25 with a floating rear end, not fun to drop off the drums to have a look.

Any ideas?

[3r!c84]

bad metering valve.

[85burb]

Are they over adjusted. Mine did that. Backed them off a bit and no prob ever sence.

[kelsfine69]

Look for oil on the backing plate, if the seal is leaking the shoes are contaminated and they get grabby

[motornut]

thats what happened to my 85.....axle seals leakin.....went for a whole rear rebuild....found i think the carrier was welded too(not why it leaked).....in my case case i found offset axle bearings to replace the old ones....

[James McClure]

Mine has the same lock-up issue. Brakes are in good shape with no fluid leaks & adjusted properly. Height sensing valve is new and in correct position, BUT, it only happens once or twice when I first start out. The rest of the day it's fine. The drums will get a light rust coating when it's damp out and the truck sits for a few days. The first few stops cleans the rust off and the issue goes away. If you have a fluid leak and don't know if it's brake fluid or rear end grease, here's a trick. DOT3 brake fluid is water soluable and rear end grease isn't. Get some of the wet stuff on a finger and wet it. If it rinces off easily it's brake fluid, if not, rear end grease. This won't work with DOT5 though, as silicone brake fluid isn't water soluable. jim

[LONGHAIR]

No matter how "fun" it may or may not be.....You still need to pull it apart and have a look. It could be anything from a seal leak or wheel cylinder leak to a spring failure or a lining problem. You could even have an E-brake sticking.

[Desert1957]

Originally Posted by James McClure

Mine has the same lock-up issue. Brakes are in good shape with no fluid leaks & adjusted properly. Height sensing valve is new and in correct position, BUT, it only happens once or twice when I first start out. The rest of the day it's fine. The drums will get a light rust coating when it's damp out and the truck sits for a few days. The first few stops cleans the rust off and the issue goes away. If you have a fluid leak and don't know if it's brake fluid or rear end grease, here's a trick. DOT3 brake fluid is water soluable and rear end grease isn't. Get some of the wet stuff on a finger and wet it. If it rinces off easily it's brake fluid, if not, rear end grease. This won't work with DOT5 though, as silicone brake fluid isn't water soluable. jim

I know you guys will all have your own fix for this problem , but here is what fixed my truck. Yes it was something you would never suspect causing the problem. What fixed it was just having the rear drums resurfaced , Yes take them off have your local machine shop or anyone that has a brake lathe with the proper adapters cut them.

The only thing that I could figure is that shiney mirror like glaze the get over the years causes the first few stops to grab and in my case lock up, it would skid the rear tires. My truck would almost throw you through the windshield until they got a little heat in them. Trust me this is your problem if there are no fluid leaks on the shoe surface this will cure it!

Desert

PS: My 83 has the 8600 GVW pakage with the same floating rear you have

[Mike_D]

I was having the same problem, here was my fix: rear axle seals were bad and the one the wheel cylinders was also bad. Additionally i noticed that I was losing a small amount of brake fluid. I thought it was leaking out the cylinder but in actuality it was leaking into the booster. That was also replaced, now it drives great.

my truck: 77 c20 with floating 14 bolt 4.10 gears

[turner15]

well my seals were done about 5 years ago, when I owned it the first time, I just re-bought it. My drums were turned then too. Guess I'm opening it up, once I find the wheel lock key!!!! dam kid I sold it to lost it...