Perhaps a moderator will move this thread from ENGINE into AXLES + BRAKES.
Are you sure you have them in correctly?
You have a "Leading shoe" and a "Trailing shoe"
They are not the same size but you can install them backwards.
Let's be careful with terminology. The hateful, crappy 254mm (10") brakes are described by GM as "Leading/Trailing Shoe" drums. The four shoes (two on each side) are identical in lining and backing-plate.
The larger, 11.x" and 13" drums are Duo-Servo, and have
primary and secondary shoes. Primary shoe has the lining facing the front of the vehicle, secondary has the lining facing the rear of the vehicle.
Primary shoe tends to have shorter, lighter-colored, thicker, and/or softer lining.
Secondary shoe tends to have longer, darker, thinner, and/or harder lining.
The backing plates are the same, but the linings are different.
Did you make sure that your backing plates dont have deep wear grooves in them that cause the shoes to hang instead of releasing?
Pretty common problem.
Yes.
Did you clean the adjusters and make sure they work without binding?
He says he re-adjusted. They can't be seized. Might be binding, or have worn teeth on the star-wheel...but none of that is likely to cause the problem described.
I would be looking at two things:
1. Restricted rear brake hose (or crushed tubing on the rear brakes)
2. Master cylinder primary piston not fully retracting to it's at-rest position. Possibly caused by a misadjusted brake-pedal-to-booster pushrod; misadjusted/incorrect booster-to-master cylinder pushrod; or incorrect master cylinder.
I think based on your brake light that you might have air in the system and your wheel cyliders are not releasing.
Air in the system might cause the dash light issue. It would be more likely to prevent that hydraulic system from APPLYING the brakes, than to prevent it from releasing.
And the parking brake cable on these trucks are a pretty strange setup.
You pretty much need to take it all apart and clean it and make sure it works.
Brake light being on forever means youve had a brake problem forever.
It is related.
Most (NOT all) of the problems I see on these trucks with the brake warning light on the dash, is due to park brake cables not moving freely in the sheaths. Specifically, the front cable connected directly to the park brake pedal. Grabbing the cable under the driver's door, and pulling it sharply will take up the slack,
lift the park brake pedal to it's proper "released" position, and open the switch for the warning light. (GM saves fifty cents by sharing an instrument cluster warning light between the park brake switch and the hydraulic system safety switch.) Any--or all--of the cables can be sticky/seized in the sheaths and causing problems. If the rear shoes on a Duo-Servo brake are not resting on the anchor pin at the top, the park brake is probably seized part-way "on", or the cables have been adjusted too tightly.
Always assure that Duo-Servo shoes rest on the anchor pin, adjust the service brakes first, then adjust the park brake (if needed).
