Brake fluid is Hygroscopic. It absorbs moisture. Okay you say, but it's a sealed system? No, it's not, the cap is vented, so air can enter, preventing a vacuum. This small amount of air contains moisture. Factor in temperature changes, leading to condensation in the master cylinder, and it's actually quite a large amount of water that the fluid is exposed to, relatively. Now, this water reacts with the metal parts in the system, corrosion for aluminum, and rust for steel. Eventually these contaminates settle in the lowest parts of the system, the lowest part being the calipers. Over time, given enough moisture, this can lead to pitting of the calipers and wheel cylinders, and sometimes brake lines( leading to failure from the inside) If it gets bad enough, a seal will tear, and the part fails. Granted, this generally only happens over years of neglect. Brake bleeding is routine maintenance, once a year is good, but even every couple of years is fine. The muck you see come out is the stuff that has settled, it's corrosion/rust. Brake fluid that contains water also compresses more than straight brake fluid, resulting in a soft feel to the pedal, it also has a lower boiling point, which can get really interesting on a long downgrade hauling 8000 lbs. Ask me how I know.......
Okay science lesson over. :-)

I'm the guy that blew the windows out of the chem lab when I was 13........... :-)

 

LMAO, thats quite halarious.. After the fact of course I do know something about that.. I drive a bomb on wheels (propane truck) for a living. So I appreciate the science lesson, hopefully the new calipers and another brake bleeding fix the issue.. Im just surprised cause the calipers are only 1-2 years old.. Seems like more and more remans come from the same cores and they come out worse and worse.. Makes owning a 20 year old truck quite the PITA

 

Just wanted to follow up with you all. Ended up straightening everything out, and now I've got some serious "bite." Upgraded from the 7500gvw calipers to the 8800's, bled the brakes thoroughly, and used my infrared thermometer to dial in the drums. I also eliminated the check valve for my trans, feels like a completely different truck, thanks guys!!!

One thing thats bugging me, is my star wheel on left rear drum spins freely.. This is due to the spring (that holds the shoes together at the bottom) being too close to the star wheel and preventing the "stopper" (no idea what to call that) from sitting in the grooves of the star wheel to keep it from spinning.. Anyone have some insight on this? Ive tried moving the spring around and nothing works.

 

reverse the spring mountings. Basically, take it off, flip it around, put it back on. See if that helps.

 

The 8800 calipers fit your 1500?

 

Tried it already.. 4 different ways and still didnt get the right clearance. Both star wheels face the rear of the truck right? I notice I have another slot in the back plate of the drum to punch out another hole, dont think it will make a difference either way though

 

They sure do. The only difference in the 7500 and 8800gvwr calipers is the size of the piston being about .3" bigger. From what Ive heard you CAN'T use dual piston calipers.

Im using 2500 pads as well (which are taller and cover more of the rotors surface area). The only "downside" I can see with the 8800's is the pad that clips into the piston doesnt hold in as nicely as the 7500's. Doesnt appear to be an issue though.

 

You might have the adjuster in the wrong way. Also the adjusters are different on each side, maybe someone replaced them both with the same part, not realizing they are different.

 

See, that's what I thought too. Unless one is left hand thread, and the other is right hand threads...... otherwise, one side would be adjusting it looser......

 

I thought all 8800 had dual pistons though