Recently while under the truck, my mechanic and I noticed that the front brake pads were getting pretty thin. I knew the rotors were warped from a pretty bad braking vibration I had. Knowing the age, and mileage, I figured it would be a good idea to just go ahead and do them all.

I bought pads, rotors, shoes, and drums. I started with the fronts and encountered no problems. One of the wheel bearings was pretty bad so I went ahead and replaced them as well. Only when I got to the back did things start surprising me.

When I pulled off the drum I found surprisingly little wear, there was no groove, I did not even have to back off the shoes to get it off. There was a little brake dust, but not much. I was very surprised to find that the liners on the shoes were every bit as thick as the new ones. Both sides were like this. I cleaned everything off with brake cleaner and put it back together. Following the advice of a mechanic friend I adjusted them manually until they just started to drag.

What happened next really surprised me. With the rear axle still in the air I ran the truck up to about 50 MPH and slammed on the brakes. Without the inertia of the truck to help it along, I expected one or both of the wheels to lock up instantly, they did not. In fact they coasted to a stop after 4 to 6 complete revolutions! I can't hardly believe this is normal, but I was afraid to manually adjust them any tighter for fear that they would drag all the time.

When I put the truck back on the ground I noticed that the rear brakes were working better, at least as far as the parking brake is concerned. Typically the parking brake wouldn't hold the truck in reverse, only going forward, now it will hold both directions. I took it back to my mechanic friend the other day and had him take a look at it. With the rear wheels off the ground again they would spin just as free as possible. He adjusted them again until they just started to drag and said that this should be good enough. I told him that I actually had them a little tighter than that before and he was very surprised that it wouldn't lock them up.

The only thing we can really think of is that maybe the shoes weren't really "centered" inside the drum, and by adjusting them as such, only the fronts or rears, are dragging and after several applications they work slightly more towards center. Neither of us can believe that Ford would have wasted the time to install ABS brakes on the rear axle if it's not even capable of locking them up while free spinning. Even the non power assist brakes on my dad's 1946 will lock up the wheels if they're in the air. Everything about these brakes seems to work, but obviously not well.

Is this a case of off center shoes and malfunctioning auto adjusters, or do the rear brakes just suck that bad? I find it nearly impossible to believe the latter. Is it possible that the pads could be so glazed that they would work no better than this?

Thanks

 

even if the pads were super glazed they should still do something. i would check the wheel clyinders, take off the brake line and see if you even have fluid (this is a pain as you will have to bleed the brakes), you proportioning valve could also be stuck to where it is only working the fronts and possibly causing your severe wear up front? Your test by putting the rear and running it up to 35 and slamming on the brakes interested me so i just tried it my rears locked right up.

 

Remove the drums again and push the shoes front to back and back to front you will see the wheel cylinder shift a little to make sure it isn't siezed up also.

 

thanks osprey i guess i forgot to tell him how to

 

I know they are working some because it will eventually stop the wheel, and you can't turn the wheel by hand while somebody is holding the pedal. I would think this would indicate that I am getting fluid, but maybe only one pad is moving. I'm thinking maybe one is seized and the other is moving, or they're both only moving a very little bit. I suppose a closer inspection is warranted.


Do you know where the valve is on these? On my Corvette it's an integral part of the master cylinder and there is an interchangeable bias spring that you can use to adjust the front / rear pressure. My mechanic said somebody told him that the proportioning valve near the rear axle was a source of trouble in his experience. However, he could not remember at all what model / year truck he was referring to.

Good to know it is possible for it to work that way. I was talking to a friend of mine who had owned two of these trucks and said that his always behaved like mine and he considered it "normal." I guess having two that worked that way might make it look normal, but I have to believe that rather than being "normal" it might just be a common problem. I'll try to give it another look this weekend and see what I can come up with.

 

im not sure where the proportiioning valve would be located on our trucks but i will look at alldata at work tomorrow

 

Yikes! The rears may have been dragging a little after my friend adjusted them. I typically get ~320 miles on the rear tank, I only got 280 this time! I guess I'll need to get it up in the air tomorrow and see if they're still dragging.

 

You may want to start by replacing the cheap items on the rear brakes - wheel cylinders, springs, and star adjusters. When bleeding the brakes after replacing the wheel cylinders, you can tellquickly if there is a "blockage" in the rear brake lines, such as a crushed line, brake hose that is restricting flow, or a bad proportioning valve.

Make sure you grease up the moving parts too, so they last a couple of years.