It's not an upgrade. If you want the GMT800 master, you need to swap the whole brake system over, otherwise you can set up a brake system with a firm-feeling pedal that fails on you in an emergency stop.
Bite the bullet. Pull those drums off.
Brakes driving me insane
- Thread starter ArthelWatson
- Start date
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Yes. You bought the lifted truck. It may be a PITA to pull the drums but you bought a lifted truck and now have to live with what comes with that truck.
A picture tells a thousand words.
ArthelWatson
Newbie
Thanks for all the replies. I'm still new to vehicle maintenance so I am definitely still on the upward trend as far as learning goes.
Yeah, I think I'll just suck it up and pull the drums and adjust them.
Took me three days last time, here's to hoping I can get it down to two on this go-around.
Does anyone have any recommendations for quality boosters? As mentioned in the original post, I learned the hard way that vehicle parts you can haggle on are not to be trusted in terms of quality.
Regarding the GMT800 master, I was unaware that it was not an "upgrade", thank you for informing me.
Also, as for the lift height, how do I properly measure that? I figured taking a tape measure from the top of the wheel to the lip of the wheel well made sense for that, what's the most accurate way to get a real number?
Yeah, I think I'll just suck it up and pull the drums and adjust them.
Took me three days last time, here's to hoping I can get it down to two on this go-around.
Does anyone have any recommendations for quality boosters? As mentioned in the original post, I learned the hard way that vehicle parts you can haggle on are not to be trusted in terms of quality.
Regarding the GMT800 master, I was unaware that it was not an "upgrade", thank you for informing me.
Also, as for the lift height, how do I properly measure that? I figured taking a tape measure from the top of the wheel to the lip of the wheel well made sense for that, what's the most accurate way to get a real number?
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.
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.
Bench bleeding takes more time 'n' effort than most folks realize.
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".
Bled after installation, of course?
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.
HELL, NO!
First Guess: You can put the original right back on. Kinda guessing you can go ahead and reinstall the ABS, too.
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.
Last edited:
IROCZSPEED
Newbie
I've been scouring these threads for ideas on how to make my 98 k1500 stop better. Think I'll just use quality pads and maybe upgrade front rotors. It stops beautifully compared to my old 94 k1500. I've just been spoiled by a 2013 and 2016 k1500.
Anything that has hydro-boost and/or bigger brake system, is gonna stop better.
What brake option number? Guessing JB5, but it would be nice to have confirmation.
MOST K1500s have crappy 254mm (10") leading-trailing shoe rear drums. Best thing you can do is to change to a 6-lug K2500 axle of the same gear ratio. You get rid of the fragile 8.5" ten-bolt in favor of the MUCH stronger 9.5" axle, and you get the much better 11.x Duo-Servo rear brakes.
The 11.x rear drums made more improvement than upgrading the calipers and rotors on my '88; and what your truck has for front brakes now is what I upgraded to.
IF (big IF) your front brakes are working properly, there's nothing wrong with what you have. More aggressive brake pads may be of some improvement, but the JB5 calipers, rotors, master cylinder, and booster are just fine as-is.
I think it's your rear brakes that are letting you down.
But that assumes that the master cylinder, booster, and front calipers are working as-designed; and that's not guaranteed...yet.
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