2005 and later SD park brake slipping

jimmy57 · October 3, 2015

I have two of these trucks, specifically 2006 year model, and I work on others. I park on a little bit of a grade and I am faithful about setting parking brake since plastic bits on shifter cables give me a little scare. Many of the ones I see, and my own, have slipping auto adjust park brake pedal assemblies. If you just push it with foot as normal the pedal will go way down and stop but truck can creep. If you push a bit then pause, push a bit more then pause, and then go the rest of the way the pedal will go firm with maybe 2 1/2 inches of travel and truck holds. The fact that diddling the pedal gives you a good hold tells me that park brake shoes and drum are OK.

Has anyone else noticed the same thing?

I tried lubricating the drum (drum? cable spool?) that wrapped spring binds on and that was temporary. I later tried brake cleaner spray to see if making the drum grippy helped and again it was a temporary solution.

The pedal has a stop that is a bit off the floor so you can think it is OK since pedal stops at a reasonable height but it doesn't hold enough that the truck won't be a bit bound in Park so that it takes that extra effort and you get driveshaft clang when you move out of park. I apply park brake before I put gear lever in Park so when park brake is working those trucks come out of Park easily and then I release park brake.

Keith Browning · October 3, 2015

What models? 250/350 or 450/550?

jimmy57 · October 4, 2015

250, 350, and 450.

I have a 350 and a 450 that I own and I see no difference in the parking brake pedal assemblies.

The issue I am posting about is definitely a problem with no travel at cable when pedal is pushed a distance. I can look from lower edge of dash into the assembly and see the spool/drum with a spring wrapped around it. When working properly the spool moves with first movement of pedal and when the pedal over travels without much park brake apply the spool/drum doesn't move until the pedal goes 3 or more inches down. That spool is what I have tried lubricating and also cleaning with only temporary success.

I know on my two trucks with 120K and 155K that the park brake is used a lot.

Keith Browning · October 4, 2015

The reason I asked what model is that the 250/350 series backing plates tend to rust out and allow the parking brake retention pins to pull through causing problems. In all honesty, the parting brake actuators tend to fail more than anything, slipping before gripping. You should never lube that assembly. I would verify that your cables are not frozen and that you can see movement at both levers going into the backing plates on both sides and if okay, replace the actuators. Since the trucks are high mileage it would not hurt to disassemble the brakes and inspect the parking brake assemblies as well.

jimmy57 · October 4, 2015

My only question was if this is seen very much. I know my only issue is with the auto adjuster feature of pedal slipping. The cable is definitely not moving to apply the park brakes due to the spool not being caught by the wrapped spring. The park brake shoes and drum area of rotors are very little worn and brakes hold full weight of vehicle with loaded trailers on a moderate grade where trucks will park to unload cattle and hay if you diddle the pedal to get the adjuster to catch. My thought is the spool is getting polished with use and allows the slip. The spool is greased from new, or at least the ones I have looked at. To be honest I can't swear I've examined the ones w/o a problem. I guess there is no fix for this other than a new pedal assembly.