The right rear brake on my 84 4x4 pickup occaisonally locks up on the highway when applying minimal to moderate brake pressure. Saftey issue not to mention the attention the squealing tire gets. Is this a master cylinder issue or a lspv issue? Either one need replacing?

 

If it's only one wheel it's probably a wheel cylinder issue.

 

Take the back wheels off and look... Most likely a wheel cylinder (as stated above) of possibly an axle seal leaking.

Are the rear shoes even any good???

 

The last time I checked they were good. I plan on taking off the wheel this weekend and looking again and looking at the wheel cylnder. You can feel and hear the right rear brake "slam shut" when it happens - a jolt - and grabs very hard.

I dont think it's the axle seal becasue I have had some work done back there on the rear end and all the seals were wither inspected or replaced.

I bought the truck a couple of years ago and have been in the process of some fixes, new paint, etc... The brake was grabbing them in occaison but is now getting worse.

Also, the break pedal "pressure" will vary as I drive. sometimes more soft with more travel and other time more firm and very little travel. There doesn't appear to be a leak anywhere and I rarely have to top off the brake fluid.

 

Look for rusted pivot points, etc. It sounds like something is hanging up because of binding or excessive rust. When you get the drum off, have a buddy operate the p-brake a couple of times (touching the actual brake pedal is a big no-no at this point BTW). Look for any springs not returning to semi-relaxed position, or binding or sticking of the shoes (not wanting to return after being applied). It should be fairly obvious when compared with the left rear.

 

I have having the exact smae problem with my '84 too. The right rear brake locks up. It has been getting worse over time, and it doesn't always happen. I have already replaced a bad wheel cylinder, and adjusted the lspv. would the lspv need to be replaced?

 

Mine is getting worse also. I just replaced the master cylinder to fix a soft pedal issue but still working on the right rear lock issue.

Since you are experiencing the same issue I think I will look into replacing the LSPV. Sounds like lspv adjustment and/or replacing the wheel cylinder didn't help. I priced one here at a local yota dealer at $189.

 

I replaced my master cylinder as well, and seemed to help with the problem. I did find out that both of my rear tires were locking, it was just the right rear that was locking harder. I haven't had an issue lately. I am going to adjust the lspv again by moving it up another inch or so, and bleed the brakes one more time. Did you replace your wheel cylinder? Do you have a lift on your truck? I have a three inch, and I think the springs are just wearing out and that is why when I would break, you could really feel it kick and the back would bounce as the wheels locked. Overall, I think I fixed the issue with the master cylinder.

 

i have the same issue with my 99 limited, only when its cold thought... it doesnt happen in reverse but when i put it in drive and hit the gas its ok unless i push the brake and i can feel it catch. i replaced the wheel cylinder yesterday and thought i had it fixed until after i changed the oil today and backed out of the driveway. when in drive if i press the brake from a roll it really grabs and it will will stay unless i give it some gas. after i drive it about a 1/4 mile its fine but you can still feel it grabbing harder than the left rear. any ideas?

 

wow my 84 does it too. I'm going to check the wheel cylinders tomorrow on mine and see what they look like. on my old ford it was causing my tires to lock up when the seals on the cylinders blew and were leaking oil into the drums

 

Did you guys check to see if they were out of adjustment. if they are out of adjustment you are over extending the wheel cylinder and the shoes are contacting on the top and bottom edges of the shoes. i run into this problem with forklifts. also try sanding the shoes to rough'en them up a little 200-250 grit sand paper.

 

Wheel cylinders. Mine does the same thing. Mine does it more in the ran. Mine also does it only at slow speeds I have never had it do it on the freeway.

 

Check your drums for out of round. Thats what fixed mine.

 

My '85 did this for a while, there was some pivot thing in there that was way rusted and would never return to the opened position so I just took apart the entire brake assembly and cleaned + lubed everything up real nice. I had to take a grinder to some of the parts they were so badly rusted but everything works smoothly now.

*edit*

The part that was sticking on mine was the bellcrank. The pin was so rusted that it just barely moved, even with a sledgehammer.