I just discovered last weekend that my Auto Park is not even used on my 1993 32’ Pursuit (1992 P30). I knew the foot cable seemed to be disconnected since I bought it in July but assumed my Auto Park was doing its thing since it seemed to clamp down tight when put into Park.
Last weekend while the kids were hiking in the park I decided to shut off the engine on an incline in Neutral and feel the Auto Park feature kick in when there was no power steering pump holding back the spring loaded release on the drum brake mounted on the back of the transmission. Nothing happen, well I mean I just would roll when I took my foot off of the brake when in Neutral and no engine running.
When I would push it up into park (while holding on the brakes) with the engine not running but key on the first click I could feel the pawl (which I had read I did not have on a 16K chassis P37 that had the Auto Park feature installed) engage and positively lock any forward movement. Without the engine running I could take it in and out of park as often as I liked. At the house I park on a very small incline and place a block of wood under one of the duals for extra safety. For 6 months I would start it and take it out of Park and let it roll so the large block of fire wood would be the only thing keeping it from rolling backwards and then put it back in park and shut off the engine. Now I just stop it and put under the block and turn the key one click and put it out of park while holding my foot on the brake pedal then let off the brake and let the MH roll back against the block of wood and then put it back into Park and remove the keys.
If I can get the foot parking brake working again (the drum brake is mounted on the transmission but I have not looked inside to see if it is still functional with shoes, etc.) I will be happy because the Auto Park feature can be a mixed blessing and I have a lot of info form Oldusedbear so I would be ready when I had an issue.
One factor is 18K miles ago the PO had a Goodwrench remanufactured transmission installed by a Chevy dealer who had it sent in overnight by freight when he was on a trip (I have the shop ticket). Since most of the 4L80’s go in trucks less than 16K pound rated it is a good chance one sitting in a warehouse would have the parking pawl installed. The Auto Park light burns in test mode but goes out as one would normally expect if all was working properly. Actually the Parking Brake light works correctly when its pedal is pressed or released but the cable does not do anything.
Does anyone else have a parking pawl in their P37 (91-93?) chassis? Since I have the Auto Park indicator light in the dash I would think it shipped that way new. Has anyone replaced a transmission and found they then had a parking pawl in the transmission? This spring (my shop’s bus rack is outside) I am going to have this all checked out. I want a functional parking brake before hitting the road out west this next summer. By not abusing the parking pawl it should be fine and I can learn to live without Auto Park.
You have auto-park on that model. The system even encompasses your regular brake system with a hydraulic Brake Boost also run by the power steering pump. It is possible to disengage the auto park from the large drum on the drive and use the foot operated option only. The weight of the vehicle makes the regular tranny pawl a no-no. I suspect the auto park is working to the point that if not on a incline of more than a few degrees it holds. Chances are the shop did not hook something up properly when they installed the new tranny. The linkage point where the auto park and the foot park meet is a little complicated as well as hard to see to work on it. I would try to find a shop that works on truck fleets, they should be very versed on the auto park system. Good Luck.
I have a '90 34' Pace Arrow in the same weight range that has a parking pawl and a manual parking brake. With all of the problems with auto park I have read about I would scrape it and install a manual system. I read somewhere here on how to do that. I have had no problems with the setup on my rig and it is a stock system.
"You're lucky to be alive my friend."
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wa8yxm wrote: Just because you shut the engine off does not mean the auto park would engage, at least not quickly
Though the power steering pump is what pushes it off, a valve keeps it there.
So unless you put the tranny in "park" it should not auto park, at least not quickly.
This is correct, if you shut the engine down with the shift lever in any position other than park, the autopark will not engage, the shift lever must be in park or the yellow parking brake knob pulled out (if there is one). It may be simply that the parking brake needs to be adjusted, it adjusts with a star wheel just like shoe type brakes on an automobile, the hole in the brake drum needs to be at the 12 o'clock position to access the star wheel and the brake released to adjust. If you want to try it yourself, send me a PM and I'll outline the procedure, otherwise a GM truck dealer should be able to do it for you.
First....auto park is always on by default... no matter what..keep in mind that this auto park system is designed to be fail safe, and it takes something to make it disengage... not engage... .in this case, some sort of a pump is required to release it...if you were traveling at 70 mph and shut off the ignition or blew a fuse, your drive shaft auto park brake would come on...you seem to have the best of both worlds with that foot brake and possibly the tranny pawl...as in some transition models...it very well could be, that someone has already disconnected the auto park cable clevis and retained the foot brake, so once this is established, then some adjustment of the drive shaft drum brake will be required if it's not holding now...this needs to be done whether or not you keep the auto park or not...
"We are often so caught up in our destination that we forget to appreciate the journey."
1998 36ft. National Tropi-Cal, with a tag axle and one slide, on a 1997 P32 Chevy chassis....7.4 Vortec Engine
CSpenceFLY wrote: I have a '90 34' Pace Arrow in the same weight range that has a parking pawl and a manual parking brake. With all of the problems with auto park I have read about I would scrape it and install a manual system. I read somewhere here on how to do that. I have had no problems with the setup on my rig and it is a stock system.
DO NOT scrape it! It does the job it is suppose to if all things are working. As stated, auto park will not engage completely until gear selector is placed in park. In my manual when adjusting the cable to the accuator, you put the selector in N and shut engine off. Of course, coach should be blocked to prevent rolling. Mine acted the same way when I got it. I adjusted the brake shoes and the cable going to the accuator (that big can) thing works fine. One has to take care of it as anything else for it to work properly. Do not start engine and throw the selector into drive and step on the gas, manual says to wait until the warning light goes out, then into drive. When stopping, keep foot on brake, shift to Park wait a few second for the parking brake to set, then take foot off the petal.
There are indeedy some units that came equipped with both a pawl and AutoPark, but we believe most of them were just under 16000 lbs. Where AutoPark is concerned, we NEVER say "never."
The internal leakdown rate of the earlier systems can be VERY low on ones in good shape. I've been told that some will hold in the BRAKE OFF condition for days. These earlier versions operate on just a little over 100 psi so the seals are not nearly as "worked" as the newer versions at 1600 psi.
The reason for spelling is so that all of the words don't look the same.
"Without the engine running I could take it in and out of park as often as I liked."
As Oldusedbear said, we never say never. The '92 16,000# chassis typically won't do this because it requires the engine driven pump to disengage the brake. So you either have a pawl or the later electric pump. Another (likely) possibility is that the original tranny didn't have a pawl, but was replaced with one that does and your AutoPark isn't working. It could also explain the footbrake problem. You can simply crawl underneath to determine whether or not yours was equipped with AutoPark.
"...if you were traveling at 70 mph and shut off the ignition or blew a fuse, your drive shaft auto park brake would come on..."
Not necessarily so. As Oldusedbear and others said, a properly working AutoPark would need to be placed in Park (or the yellow knob activated) to allow the spring to drain the actuator and apply the brake. Mine, for one, will hold the brake off for days with key and engine off and out of Park.
IF the engine should die (no power steering pump on models using the pump for the auto brake) the pressure holding the actuator spring compressed would not be released until the shift lever was put in the "park" position. It will NOT slam on the park brake, unless it has a deffective valve.M2Cs
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