Parking Brake

Don't know about the new auto's and can't really answer your question but why do you set the brake with it in drive?

 

Don't use the stab braking method. Adj your brakes. Downshift to a lower gear. Engine brake?

 

Stab braking puts MORE heat into the brakes than holding LIGHT & STEADY brake pressure. It would be best to use jake brake & lower gears and not touch your brakes if they would maintain a safe slow speed downhill.

Each time you let the speed build, it creates far more energy than maintaining a steady speed. The couple of seconds of no braking doesn't cool the brakes more than the increased speed will heat the brakes. Stab braking is how to overheat your brakes.

 

So one thing to remember is that your parking brakes apply themselves between 20-40psi. So the spring are only applying that much pressure to the brakes, and only the brakes that have a spring brake are activated.

that said, you may very well only have them on one axle. It’s not uncommon for trucks to be spec’d this way. One axel locked down will not hold the truck on that much of a grade, especially not with it in gear.

i’m assuming your truck is equipped with an Allison automatic?? If so, then just like your car the transmission is constantly applying power to wheels unless you’re in neutral.

**Side note some of the Allison’s i’ve driven will automatically kick into neutral when the brake is applied. Not sure if all do, or maybe just newer ones.

 

Old timers used to use a large enough rock, a wheel chock, or something else to "scotch the wheel" like a wheel chock accomplishes if they have to park on steep grades. Manual transmissions can help when parking on steep grades by shutting the engine off in the appropriate gear to aid the brakes/wheel chock holding the truck.

 

If you can't shift from drive or reverse into neutral with the parking brake applied, it is not road worthy.

If the parking brakes can not hold the truck, don't drive the thing until the brakes are fixed.

 

You should probably keep it in neutral when the parking brake is set, unless you have to keep it in drive to run the equipment (like concrete pumps do).

Yes. The pushrod pushes on the slack adjuster regardless of whether air pressure (you stepped on the brake pedal) or spring pressure (you set the parking brake) caused the pushrod to extend.