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I tried the NBS MC swap. It doesn't work with JB6 stock brakes. The pedal almost goes to the floor. With the Hydroboost, I'd have to see if the NBS hydroboost MC works, but honestly, the brake performance has been stellar with the stock hydroboost and master cylinder. I deleted the ABS anyways because the unit failed, so running an adjustable proportioning valve was the simple solution for the rear brakes.
Do you know what pressure is running to the rear? It seems the rear anti lock managed the rear pressure so as not to cross into lockup but allow maximum braking it could handle
How 'bout the holdoff valve, and the safety switch?
The valve regulates the pressure to a max of 1200psi, and generally you want around 1000 for disc brakes. Drums around 5-600psi. There are others that allow for a higher pressure than 1200, but that pressure works great. It I really really slam on it at I can lock up the rear brakes. It feels perfectly safe the way its dialed.
The main proportioning valve on the ABS unit failed. It was kinda scary. Something would get stuck in the valve, leaving me with a firm pedal and hardly any brakes. If I stopped the truck, restarted it, slammed on the brakes a ton, it would eventually start working. And because there are no new replacement parts available, and the ABS bleeding process is impossible without a snap-on scan tool, it made the most sense to remove the unit. I lost all trust in the ABS system. The ABS part of the unit worked, but something failed in the valving part. All the wiring is intact. I took the whole unit out, and removed the fuse. I ran a T connector to the front brakes and integrated an adjustable proportioning valve on the rear. Honestly, the truck stopped better than before. I also grew up driving older trucks without ABS, so it wasn't a big deal. I actually prefer a vehicle without ABS.
I dont know if you have done anything yet, but the issue you describe could easily be the rotation of the pump. DO you have the "Stock" pulley? Dropping a bit in pulley diameter will likely solve your problem. While i Dont approve of your fluid choice, cooling it more than stock should maximise your life fine. The trucks did come with dexron iii despite it not being the best fluid, i couldnt see it nuking the system. I couldnt explain the behavior after your partial flush other than the fluid you flushed carried out some contamination or varnish. A magnetic inline filter before the cooler is always wise and cooling is wiser. The pulley diameter change should be small because the pump does have a rotational speed limit , im not sure how much it is
That is an interesting thought if running a smaller pulley. My pulley is stock. I'm going to add the cooler this week, but that might be a good idea to help increase the flow at slower speeds.
