Quote:
Originally Posted by JLMounce
To play devil's advocate here, the brake sizing on those mid 90's chevy light and medium duty trucks/suv's was piss poor. Hyrdoboost isn't necessarily the issue as much as the fact that GM put brake rotors and calipers on those vehicles that were originally on late 60's to early 70's cars that weighed 1500-2000 lbs less and weren't towing trailers.
Hydroboost is one part of the brake system, it can't make up for extremely undersized brakes with sheer line pressure.
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The "big problems" with the GMT400 trucks were especially pronounced on the 1500 series; but those were by far the most-produced. There were enormously fewer 2500 and 3500 series trucks made compared to the 1500, and the heavier-series trucks also had much better brakes.
The 1500s had a crappy rear axle originally designed for compact and intermediate-sized cars. GM had no business putting it under a full-size pickup. That axle was almost universally equipped with 254mm (10") leading-trailing shoe drum brakes that require the park brake to be used in order to maintain shoe adjustment. Since nobody uses the park brake, the shoes are perpetually far from proper adjustment. Making things even worse, the front shoe on each side does all the forward braking. Which is why the front shoe will be worn-out long before the rear shoe--which does the majority of braking in reverse.
The first few years of that truck series, the regular-cab 1500s got a miniscule power booster, thin rotors, small-bore master cylinder, and tiny caliper pistons. Even GM acknowledged that the JN3 brakes were under-powered, in the early '90s they increased the braking power to JN/JB5 series brakes--what had come on the extended cab 1500s all along. But they still had the horse-crap leading/trailing shoe rears.
A rear-axle swap that replaces the junk 8.5" ring gear, 10-bolt axle with the 9.5" semi-floating 14-bolt cover axle also upgrades the rear brakes to proper 11.x Duo-Servo drum brakes where
both shoes stop the vehicle.
Don't get me started on folks who think they can bleed ABS brakes on the post-1990 GMT400 trucks without using a scan tool to chatter the solenoids.