Okay ... I SOLVED THE AUTO PARK BRAKE PROBLEM!
We have owned our 1998 Chevy chassis motorhome for about 2-3 years and have suffered the Dreaded Auto Park Failure While Driving three times. I had to come up with a permanent fix to that problem as I do not like repeating failures twice, much less three times, and I know from my research that many others have suffered the through the same Dreaded Chevy Auto Park Brake Failure While Driving.
I want a fix which would keep the auto park brake where it would be automatically engaged/disengaged based on the factory vehicle wiring.
My redesign also solves the auto park brake shoes dragging on the drum problem along with solving the insufficient park brake holding problem (my park brake never had much holding power when the brake shoes were adjust to no drag on the drum and overheat).
My redesign is a much less complicated mechanism that Chevy put in there - go here for a description and photos of my project: http://www.irv2.com/forums/downloads.php?do=file&id=275
The project been completed and put back into service, and has been tested on several camping trips.
All I can say is ... it operates beautifully, holds the park brake very tight, is so simple and is fully automatic with the factory vehicle systems engaging and disengaging the parking brake.
I was asked this question:
Q. Does your version automatically engage the parking brake when the vehicle is put in PARK?
A. Absolutely. It automatically does everything the original unit did automatically.
I made no changes to the wiring or controls on the vehicle or the wiring harness to the unit, I even adapted the original wiring connectors from the original components to the new components so the connections would match the original wiring connectors from the chassis to the auto park brake unit.
The only thing that is different is that the brake cable is pulled (engaged) and pushed (released) by a 12 volt linear actuator instead of the hydraulic cylinder linear actuator.
When you are driving, shifting in and out of Park, the park brake operates on its own just as the factory unit did.
My chassis manual states that the factory unit takes 5-6 seconds to fully engage/disengage. My redesigned unit takes about 7 seconds to fully engage - not much different than the factory unit.
I put a label on the instrument panel, under the speedometer, stating that the park brake takes about 6-8 seconds to fully engage/disengage. This is just for information of others who may drive my motorhome, the factory never had a label stating it could take 5-6 seconds to fully engage, that information was buried in the chassis manual.
Once the engaging starts you could walk away from the motorhome as the linear actuator will continue to pull the park brake tight until its internal limit switch for retraction is met; when disengaging the disengaging starts immediately and the park brake shoes keep getting pushed farther from the drum until the internal limit switch for extension is met. It is ready to move almost immediately but I wait the 6-8 seconds before driving away.
When driving off, all you do is shift out of park and the park brake releases just like the factory unit does.
When parking, all you do is shift into park and the park brake engages just like the factory unit does.