Auto brake?

[captaindesmo]

I have read some horror stories about GM's auto brake, My '92 fleetwood bounder doesn't appear to have this. Does anyone know? How can I visually check? Workhorse site says it's on 16,000lb GVW units and above.

[tomwalt]

I think GM started using this system around 1989 and for the first 5 years or so they were driven off the power steering pump. You would be in this time period.
Oemy's Web Site - Tech Tips has a good library and some write-ups on how it works. The resident expert 'oldusedbear' hangs out there as well. Drop him a quick note on what you have and he'll let you know how to test it for issues. Ask him to send you the 'gennie light' directions so you can build a monitor.

[edgray]

Quote:

Originally Posted by captaindesmo ......... My '92 fleetwood bounder doesn't appear to have this. Does anyone know? How can I visually check? ........

Is your MH built on a CHEV P-32 chassis? If yes, read on. If no, the answer is "no, you don't"

Do you have a foot applied parking brake? If yes, then you don't have an AAPB (which is a good thing).
Ed

[captaindesmo]

Yes, I have a foot operated parking brake

[max49]

Quote:

Originally Posted by captaindesmo Yes, I have a foot operated parking brake

If a foot operated paring brake is good enough for cataindesmo, why did they come up with the engineering marvel brainstorm of the autopark?
It would interesting to know who invented the GM AAPB and if he still works for GM or has since went to work for Workhorse or Actia?

[DriVer]

Quote:

Originally Posted by max49 If a foot operated paring brake is good enough for cataindesmo, why did they come up with the engineering marvel brainstorm of the AutoPark? It would interesting to know who invented the GM AAPB and if he still works for GM or has since went to work for Workhorse or Actia?

Max, Over the 10 years that we have been talking out this let me again write out the reason why your vehicle is equipped with the dreaded AAPB.

The 4L80e and the 4L85e when equipped on certain Chevrolet and Workhorse model motorhome chassis whose weight (GVWR) of greater than 12,301 pounds but less than 18,001 pounds are all equipped with the J71 or the J72 AAPB depending on model year.

The reason for the AAPB is because GM did not rate the transmission case for use with a parking pawl for the weights described in the previous paragraphs. Absent meeting the rating and requirement, GM had to make a parking brake that would hold the full weight of the vehicle on a test incline for a specific amount of time. Having exceeded that specification GM was awarded a certification to sell the vehicle.

Some of the very best talent that supported the AAPB for WCC and Chevrolet have since retired. I'm not sure if the guy that made the AAPB for GM has passed away or not but it's been a long time.

The foot apply parking brake was installed and rated for weights of less than 12,300 pounds but that was it. All WCC motorhomes (any GVWR) that have a foot apply parking brakes have parking pawls. Absent the parking pawl, the vehicle will have an AAPB whether its a P series (all) , W24 (early) or UFO (HPB).

Many commercial vehicles from Hertz & Penske (others) use AAPBs as well. It is quite a robust system and when it works it works well. The trouble is getting it to stay working due primarily due to electric hydraulic switches and cascading downward as you know to the other more costly components.