[70GMCer]

If the prop valve is stuck, clamping that pin/rubber plunger will not work. I've been told to drive the truck to around 10 or 15 mph and then slam on the brake pedal hard. This will most likely release that valve. You might have to do this a couple times. I didn't know about this until someone on here told 70c10 to try that. Damn if it didn't work. Then bleed the brakes. Also, the dash brake light will stop coming on.