Why do AutoPark parking brake systems even exist?


On a pretty regular basis, I am asked to explain why AutoPark systems even exist. In the same vein, many users ask if they can switch over to an all manual system – – either a foot pedal or hand lever type, and disconnect the automatic apply (AutoPark) portion of the system.

We should start by explaining that most AutoPark systems built between (approx.) 89, and 98, do indeed have a foot pedal means of applying the parking brake – – as well as the “P” position on the shift lever – – aka PARK – – which is more accurately described as AutoPark.

That same P position which we have seen on the family car for years (at least all the cars with automatic transmissions), is provided as a system to keep the car, or motorhome, from rolling when we are parked – – especially on some kind of incline. However, it turns out that all P’s are not created equal. In the family car, when you put the shift lever into PARK, you are actually engaging a mechanical pawl device within the automatic transmission. These pawls work quite well unless you jam the shift lever into PARK while still rolling at several miles per hour – – in which case they will normally break, and the vehicle will continue to roll unless you do something.

It turns out that GM builds their transmissions with pawls up to about 16,000 lbs. GVWR. For reasons I don’t know, they do NOT apparently build them for vehicles OVER the 16,000 lb. figure. Allison, on the other hand, builds locking systems that go to 26,000 lbs. What motivates either company is something to which I’m not privy.

I’ve always made the assumption that GM designed the AutoPark system to make you think you were in the family car. Most motorhome drivers are NOT truck drivers – – Most have never driven heavy vehicles until they got a motorhome. Sooo – – To ease the transition, the manufacturer continued to include the PARK position on the shift lever. Come to a stop, stick it in PARK, and walk away – – just like the family car.

This is where AutoPark comes in. Instead of having the locking pawl system which is not strong enough for the heavier RV, they have designed mechanisms (several different ones, actually), which will automatically apply a fairly good sized parking brake – – located on the driveshaft, right behind the transmission. As mentioned above, some of these systems also have a manual means of applying this brake – – as well as the AutoPark. From about mid 98 on however, the only parking brake function is provided by the AutoPark – – No foot pedal or lever.

PROBLEMS: All the different versions of AutoPark have their own peculiarities and tendencies to fail. We won’t go into all of that here – – Suffice to say that they do fail, and frequently in a manner that locks up the parking brake – – In the fast lane, your driveway, wherever. This, along with a lack of readily available service (my opinion), has led many people to ask if they could disable the AutoPark and go to some sort of completely manual system.

The short answer is YES. BUT, there are additional considerations in my view.

1. Some states require inspections of motorhomes. I’m told that most will not pass an intentional disconnection or modification of any OEM brake mechanism. So it is conceivable that you HAVE to have a properly working AutoPark to pass the inspection and get your license. I’d hasten to say that I have not studied this situation – – I don’t know which states have these requirements, or any of the fine print contained therein.

2. I’m not a lawyer, but I’ll bet my Dead Frog and Bottlecap Collection that you are getting into possible liability issues if you disconnect your AutoPark system. Someone not familiar with your RV sticks the shift lever into PARK and walks away – – not knowing that is has been intentionally disabled. Just guessing, but I’ll wager that a jury of your peers will examine the depths of your pockets and may well find you liable for some ensuing accident or injury.

I would again stress that the above is simply my opinion. But I would then add that AutoPark systems are not all that difficult to troubleshoot, fix and maintain. You certainly wouldn’t believe that in the face of all the horror stories you hear about incompetent service, over charging etc. There is apparently a horrible lack of people who really understand this system, and are willing to repair it at a reasonable price. As an example, automatic transmissions are far more complicated than AutoPark, and you can find good tranny wrenches most anywhere – – Not so with AutoPark. Far too many places simply throw parts at the problems until they get lucky and get it fixed. Almost nobody is willing to troubleshoot to the component level.

So – – Bottom line: We advise folks to learn about their AutoPark. Almost anything that goes wrong with it, is something you can fix yourself if you are OK with some straightforward mechanical work. There are things to watch for, and some recommended (not too spendy) spares you can carry. Our AutoPark Library is available for information, and we can walk you thru just about any procedure you may encounter.

As always, questions and comments are welcome. We enjoy hearing from you.

Roger – – aka oldusedbear at the AutoPark Library

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