I had a problem with Brand F rear wheel cylinders rusting up. The brakes acted weird, with "variable" pedal travel (sometimes better than others), but they worked perfectly after both wheel cylinders were replaced. It was close to twenty years ago, so don't expect me to remember much more than that.

I rolled in a bit of brake adjustment today. It's hard to check the drag because of the locking rear end. Turn one 80 pound wheel with it's 90 pound hub/drum assembly and you're turning the opposite side, gears, and the crazy long drive shaft.

The adjustment brought the pedal back nicely. It was consistent all the way home. Another panic stop gave proper performance.
Sadly, I dialed in a wee bit too much. About a mile after the 45 mph panic stop and sitting in the driveway for a few minutes the left rear drum was 300 degrees. The right rear was 200.

I need to pop the axles out and set the brakes again. That's the only way I can think of to get it dialed in properly.

I couldn't get the adjuster to back off so I had to pull the drum. One of the pads has a broken lining and a hold down nail is missing. The spring that holds it fell out of the drum.
There is a rub mark on the side of the pad and a light rub mark on the drum beside the braking surface but I'd rate it as cosmetic at this point.

I guess it's time for pads and a hardware kit. Might as well throw cylinders at it while I'm in there. I'm sure they're full of the same nasty stuff that crapped up the front calipers.

Feets it sounds like you've got it! I thought the symptoms did not make sense to some extent but I dont know ABS so that was as far as I could go speculating

I installed the rears and, naturally, there was a bit of trouble there too.

One new wheel cylinder had imperial mounting bolt holes but a metric fitting. That was a no go. A coworker and I jacked around with that for some times before I figured out the problem. It took another day to get things sorted out with the parts store.

Once that was resolved, installed the hub and drum assemblies. On full floating axles it is best to set the drag before installing the axles themselves. Otherwise, with that locker back there spinning one side involves shipping both 80 lb hub/drums both axles, the Dana 70 center section, and that crazy long driveshaft. Not the best idea when looking for a light drag. The truck sat on the lift at work for a couple days because I couldn't get the brakes bled.

I tried gravity bleeding, using my new Mity Vac (old one was sketchy), and even the vacuum bleeder the guys use in the shop. After running a quart of fluid through it I still couldn't get a good pedal. It still went to the floor. It seems those methods simply didn't move enough fluid quick enough to remove the air. After work on Saturday, I got a coworker to stay late and help me bleed them old school.

That worked and I drove the truck home. The brakes don't feel as crisp as a new car but I suspect they never will. Still, when some high school kids in a Honda cut me off I was able to hammer the brakes and bring the truck to a respectable stop.

I proclaim the old truck to be ready for a road trip. Naturally, I called the seller of the machine to accept their counter offer and they sold it the day before. There is no need to take the truck to LA now. It looks like I'll be in my 200 instead.

Kinda disappointing, but no big deal. It just means I'm not spending that money and can enjoy the road trip a bit more without lugging that thing around. Leaving the 19 mpg truck home and taking the 30 mpg car (with better A/C and radio) isn't exactly punishment.

Feets another deal will come along in short order, one that you just cant pass up! You'll get your (loaded) trip