Brakes Grab Rough

[oldjohnny]

I've been having this problem lately and it is a hazard when the roads are wet. Everytime I apply the break, my truck starts to brake normally, but right when it is about to stop, it grabs on very rough.

I started with changing the calipers. I changed the Drivers side one week and that seemed to have fixed the problem. I Drove the truck 100 miles back to school and 2 days later, the symptoms came back. I came to the conclusion that maybe the other caliper needed changing as well. A couple of weeks later, I went home and changed the other side, but no difference.

Anyone know what the problem is? Could it be that the same driver's side caliper went bad quickly? I did buy it at O'reilly and everything I buy at O'reilly tends to go bad quickly. I'm going to buy another driver side caliper and see if this fixes the problem, but if it doesn't, what could the problem be?

 

[Earl43P]

I wouldn't replace the caliper yet.

Does it have ABS? IF so, pull its fuse(s) and drive it. See if it quits.

Try putting the parking brake on about 3 or 4 clicks while approaching a stop, just enough where you feel them dragging. That should make the brake pedal feel higher. See if that affects the grab when you stop.

Go in reverse at a good clip, slam on the brakes and see which lock up, and when. Investigate the wheel that won't lock up. You should have inspected the rears already, but these tests will show a problem back there.

 

[oldjohnny]

I wouldn't replace the caliper yet.

Does it have ABS? IF so, pull its fuse(s) and drive it. See if it quits.

Thanks for the advice.
I tried pulling the fuse, but had a problem. I went to the distribution box and the slots for the ABS are empty (no fuses). Are they located somewhere else? I tried looking for the relay, but couldn't find it either. I know the truck has ABS (at least rear only) since I can always hear it work.
I tried the hand brake technique, and the pedal did feel a bit higher, but the brakes still grabbed hard.
I went on reverse, and the brakes didn't grab on hard, but the rear tires lock up.

The main problem that I have with the brakes grabbing too hard is that they will make my tires screech (always the back ones). In the rain, driving the truck is a big risk. My stoping distance is greatly reduced because ABS will always engage. When it is dry, my ABS will engage on some stops, but not as bad as in the rain.
At this point, I'm going with a bad Master Cylinder. Since I have replaced both rear wheel cylinders for the drums and calipers once, I suspect the problem is that my fluid is being "over-pumped". Any suggestions? Should I drain the system before changing the master cylinder?

 

[Flat Toy]

Have you made sure that there is some lube between the rear shoes and the backing plate. If they are dry the brakes will lock up like that.

 

[nitrofan1]

+1....Clean & adjust the rear. It might be advisable to replace the springs & such on the rear. It amazes me all the time when people come into my store, buy brake shoes and don't get a spring kit. Less than $10 will triple the life of the shoes and help the brake feel.

Course one other option is a brake hose has failed internally, especially if they are original units.