Restoring RWAL

[Steven Petersen]

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Today I’m finishing up my RWAL restoration. After I bought this 88 a year ago, I noticed the brakes weren’t right. Front pads were like new. Rear shoes were low, I replaced with Delco. Better but still poor pedal feel. I actually did the RWAL elimination hack. It made things better, but still not 100%. It’s been bugging me ever since as I like things factory. So I found a NOS GM Isolation/Dump valve/proportioning valve. It’s both units including the bracket and short crossover pipe. If this doesn’t fix it, then I will will replace the black box/brain unit.

 

[Nad_Yvalhosert]

The lousy feeling leading-trailing 10" shoes was the worst design GM ever put in those 400 trucks.
Your issue likely isnt in a hydraulic/electronic unit, it's the fact that you're only using one rear brake shoe (as designed) when driving forward.
On my '88 1500, I left the master and RWAL system intact. Instead, I eliminated the whole puny brake assemblies, by putting a 6 lug 14 bolt axle from a LD2500 on my beast. Dramatically better pedal feel, and the parking brake worked much better.

Though in all honesty, the LD2500 donated her vacuum booster at the same time...

 

[Steven Petersen]

The lousy feeling leading-trailing 10" shoes was the worst design GM ever put in those 400 trucks.
Your issue likely isnt in a hydraulic/electronic unit, it's the fact that you're only using one rear brake shoe (as designed) when driving forward.
On my '88 1500, I left the master and RWAL system intact. Instead, I eliminated the whole puny brake assemblies, by putting a 6 lug 14 bolt axle from a LD2500 on my beast. Dramatically better pedal feel, and the parking brake worked much better.

Though in all honesty, the LD2500 donated her vacuum booster at the same time...

This is a light duty 3/4 and already has the 9.5” rear end. I did that same swap as you on an 88 K1500 I owned 25 years ago. The braking improvement was huge. And I only swapped the axle, not the master cylinder or booster.

 

[Nad_Yvalhosert]

Then you must have some other problem. Have you verified that:
The front caliper sliders aren't bound up
The piston moves freely
There isn't restriction in the 3 brake hoses
The rear shoes are adjusted properly
There isn't air in the system.

Granted, these trucks are known for lackluster pedal feel, but loading up the parts cannon is never the correct fix..

 

[Steven Petersen]

New unit is installed and functional. RWAL is working properly and pedal feel is good.

 

[Steven Petersen]

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Earlier this week I installed a NOS brain unit for the RWAL. My brakes work great. The rears won’t lock up, the fronts just barely will. Great pedal feel too. I remembered these brakes working fine when the pickups were new. Even the 1/2 ton models. Eliminating the RWAL is a hack job, not addressing the real issue. You just need to find the right replacement parts.

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[haroldwca]

Steven, thank you for this write-up. My 1988 RCSB K1500 will lock the rear wheels if I need to stop quickly. The RWAL is inoperative, and I have been searching for information regarding restoring it. Almost everything I read is about deleting it. It seems that few are willing to fix the problem, but you apparently did. Now I have an idea of what components will need to be investigated.