Drum Brake issue

[engineman2]

My passengers rear brake locks up very quickly when in slick conditions. If the road is wet/it's raining or I'm on mud and I even tap the brakes the rear passenger tire will skid. I've been having this issue since I bought the truck a year ago. It had a leaking rear axle seal so I replaced that and in the process rebuilt both drums (springs, adjuster, wheel cylinder, etc.) and put on new Napa shoes. Afterward I bled the brakes according to the TM. I was hoping this would fix it. It didn't so I bled the brakes again and took off the offending drum twice to try and figure it out. I couldn't. So, I think it might have something to do with this rednecked proportioning valve riser that someone made when they lifted the truck. It has a 4" lift and, as you can see in the pictures, the bracket sure hasn't been raised 4 inches when compared to my 4" long Leatherman. I would think this should give me less braking since the valve would probably be less open when farther down. I'm at a loss. Sorry this was so long but it helps to be thorough. Hopefully ya'll can figure this out, Thanks.

 

[rchalmers3]

I don't think the problem would be the proportioning valve because it would affect both brakes.

Some possible causes I can think of off the top of my head are:

* Brake drums cut to different diameters
* Wheel cylinders of different diameters or not moving equally
* Shoe set not installed correctly (one side with both leading shoes, for example)
* Incorrect adjustment (probably on side that is slower to apply)
* Restriction of fluid to side that is slow to apply (crushed tube)
* Air in system

It may help to have soldier "B" apply the brakes slowly while you rotate the rear wheels by hand to see if you can duplicate the quicker application on one side. That way, after you discover the cause and remedy it, you will be able to confirm the rear brakes apply equally.

Too bad nobody invented a set of brake hydraulic pressure gauges for the 4 corners.

Good luck with your braking issue and let us know what you find.

Rick

 

[engineman2]

Thanks Chalmers. I had figured it would equally affect both sides if it was a valve issue but wanted another opinion. I've bled the brakes several times so there better not be any air. When I rebuilt the drums I put on new Napa cylinders on and made sure to put the bigger shoe on the trailing side. Unless I got a bad (new) cylinder and happened to put it on the same side I doubt that's the issue. Another bit I forgot to add was that the pass side drum gets much hotter when driving than the drivers which leads me to believe that the pass side auto adjusts too far out. I've rebuilt the adjusters and taken them apart a few times to be sure they are correct. I've also slackened the parking brake cable to see if that was the issue to no avail. Maybe my drums are different diameter. That'll be fun.

 

[319]

I'd lean towards the incorrect shoe installation first.

It appears i'm a little slow today.

 

[porkysplace]

Are the backing plates wore where the shoes ride ?

 

[doghead]

A bad axle oil seal will cause the issue you describe. I'd look at the shoes again.

You did replace them, right?

 

[engineman2]

When I mentioned parking brake in my earlier post it got me thinking that the cable does not end at the adjuster by the fuel tank. So, I ran the truck to the shop, conveniently located 200 yards away, and put it on the lift and guess what I saw...the shroud the cable runs through was pulled away from the backing plate and the cable was pinched by the clip that is supposed to hold the shroud on to the plate. My guess is somewhere along the line the cable snagged on something offroad and got pulled from the plate and pinched itself. I poked the old clip out of the way and the cable went into the drum more than it was already. I also took off the inspection plates and looked at the shoes. From what I can see the thicker shoe is on the trailing end so hopefully I don't need to remove the axle and all.

I took the truck off of the lift and ran it down a slick trail by the river and it didn't skid when I hit the brakes, so I think that dumb little clip might have been what was wrong. Hopefully that fixed it, next time it rains will be the real test. Thanks guys for all the responses.