97 K1500, 4x4, Dana 44E front axle
I got to bleeding and replacing the brake fluid... ...Bled fine, put new fluid in, all of a sudden no pedal! So I bleed again. And again. And again.
Vacuum bleeding is specifically not recommended on these vehicles. Pumping the pedal, then jamming it down with a rod propped against the seat should work...but would take forever, and will create problems if the rod you jam in place falls out while the bleeder screw is open. I have had success with gravity bleeding for minor work at or near the wheels; and pressure bleeding for major work, or work near the master cylinder.
Unless the brake hoses are leaking, they're not the problem with a low pedal. Brake hose problems (plugging) tend to either keep the brakes engaged; or they result in a high, hard pedal because no fluid can flow through them. Worn-out brake hoses can expand under pressure...but not so much they're going to cause the pedal to drop that much. You might notice a MINOR improvement in pedal feel when old hoses are replaced with fresh, new ones.
That all assumes that the master cylinder is full of fluid--
no trapped air pockets. And that means a THOROUGH bench bleeding,
maybe followed by on-the-car bleeding of the master cylinder by connecting the two brake tubes, unbolting the master from the booster so the master can be tilted "down" in front, and tickling the primary piston until all the air releases into the reservoir via the drilled ports. Since the brake tubes are already in place, no additional air is drawn back into the master cylinder.
I try to bleed the ABS. Did that 6 times, no dice. So I pulled it and plumbed in a Wilwood proportioning valve, bled another couple times, still no pedal.
The ABS MUST be bled with a scan tool. If you didn't use a scan tool, you didn't bleed ALL of the ABS. See attachment, below.
Did you disable the metering/holdoff valve, or the safety switch?
Ditching the ABS without proper diagnosis seems like a silly move, and one that didn't fix the problem.
Bought a new master cylinder, bench bled it, put that in. No change.
Bench bleeding takes more time 'n' effort than most folks realize.
Figured, what the hell, burning money on this anyway, got a new booster and put that in. Nope.
Boosters don't make the pedal go to the floor. Pedal to the floor is virtually always "air in the system". Sometimes is an internal leak in the master cylinder, but you've got the same low pedal with multiple master cylinders...so I go back to "air in the system".
Figured, oh jeez, maybe it's the drum cylinders? So, I swapped those out. Also, no.
Bled after installation, of course?
I'm here now feeling dumber than a sack of pebbles and 2 months in to a "project" that should've taken an afternoon.
BT, DT. A guy feels like he should be wearing a Special Olympics T-shirt and carrying a trophy. NOT a situation I'm comfortable with, but it happens.
Considering an upgrade to a GMT800 master
HELL, NO!
and a new booster (the Chinese one I bought broke).
First Guess: You can put the original right back on. Kinda guessing you can go ahead and reinstall the ABS, too.
HOW DO I GET TO THE ADJUSTERS IN THE DRUMS? THEY'RE IN THE MIDDLE OF THE DRUM!
You had the drums off to replace the wheel cylinders. You already know how to get to the adjusters.
You have the craptastic 254mm (10") leading-trailing shoe rear brakes attached to a shiity 10-bolt rear axle. I am infamous on this forum for my total disregard and lack of respect for both the leading-trailing shoe drum brakes, and the fragility of the OEM 10-bolt differential in either open or Gov-Lock versions. HOWEVER, that's not the source of your issue provided the wheel cylinders are functional and the shoes are properly adjusted. One downside to the 254mm drums is that they're perpetually mis-adjusted (too loose.)
AFTER you manually adjust the rear brakes, you'll want to use the park brake frequently to keep them in adjustment. Which means the park brake cables will likely need to be replaced because they've seized from lack of use.
The 10-bolt 8.5" rear axle is a hot mess on a stock truck. Adding a lift and big tires is a recipe for disaster.