I am really going crazy here. I have posted in the past about this great driveline brake that GM installed on this 1990 Pace Arrow on a P30 chassis. I have had a great deal of trouble with it, especially the shift actuated control valve. If any of you have the Chevrolet Motor Home Chassis Service Guide I am lookinig at page 6-10, Figure 6-10. I have had to replace the mentioned valve several times now and at $100 I am looking for another way to fix this problem.
What I would like to do is remove the shift actuated control valve from the system and use only the manual apply control valve. Have any of you done this and if so has everything worked out ok?
I am also somewhat confused, easy to do, about the proper fluid routing should I do this.
Any other suggestions would be greatly appreciated!!
1991 P30 454 TBI 32' Pace Arrow
Lon, Kathy, Shaelene, Brielle, Kyle
and Cooper, our Lhasa.
Thank-you for your replies and suggestions. I, as well as many others, am very frustrated at this wonderful system G.M. installed on this coach. I am somewhat surprised there has not been a HUGE recall on it. I know that there was some kind of a recall on part of the system, but it seems the whole system ought to be recalled.
Anyway, as Todd suggested, I have already been studying the illustrations on Figures 6-10 through 6-13. I am going to see a man today that might be able to help me out. On fig. 6-13 I am wondering if I can bypass the shift actuated control valve by tying the line from port B of the manual apply control to port 4 of the HR-1 relay valve. This seems as though to be an answer, but I am not positive. There is just to much monkey motion going on here!!
I have used the search function here looking for info, but cannot find where anyone has tried to eliminate a valve like this.
Keep any suggestions coming. I really do appreciate them.
Be it known, if you're looking for a low-cost solution, that the parking brake cable to fit my '91 14,400 GVWR chassis costs approx. $200 new from GM, and around $150 at the only RV Salvage yard I could find in this country that had some. (COLAW RV SALVAGE - Rt. 4 Box 515A, I-44 & 71A, Carthage, MO 64836; 417-548-2125.)
OTOH, NAPA listed a cable for around $40, but it's too short for my application. Mine calls for a 110" cable, and NAPA's is just shy of 98". It's this part
Probably the best thing you could do is call COLAW salvage yard and see what it would take to get the foot-brake and cable mechanism that they put on the 91-93 chassis (see page 6-11 of your chassis manual), retro-fit it to your coach, and disconnect the hydraulics as others have done.
Barring that, I think I'd study figures 6-10 through 6-13 for a while, and see if there is a way to remove the shift actuator valve from the flow and let the manual apply control valve control things for me. Maybe replace the shift actuator control valve with another manual apply control valve, and note which position it needs to be in difference scenarios, and figure out a way to activate them from the cockpit? (Kinda reaching here)
Edit: upon re-reading your post, I see my last paragraph is what you're talking about doing. Hopefully someone will eventually chime in who has done it before.
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I have checked into retrofitting the older hand lever and cable system to the parking brake and scrapping the autopark system. All the parts necessary are available from Chevy truck dealers. You will need to know the approximate length of the cable you will need as there are different lengths available.
A bit of a diversion, but the '90 P30 auto-park does have a recall. You should check to see if yours has been updated. Here is the text of the recall:
Make : CHEVROLET
Models : P300 Years: 1990
NHTSA CAMPAIGN ID Number : 94V183000 Recall Date : SEP 27, 1994 Component: PARKING BRAKE Potential Number Of Units Affected : 3762 Summary:
THE AUTO APPLY PARKING BRAKE SYSTEM FAILS TO RELEASE THE PARKING BRAKES AFTER ACTION HAS BEEN TAKEN TO RELEASE THEM OR THE SYSTEM MAY AUTOMATICALLY APPLY THE PARKING BRAKE WHILE THE VEHICLE IS IN MOTION. IN EITHER CASE, IF THE DRIVER DOES NOT NOTICE THE TELLTALE RED BRAKE LIGHT AND STOP THE VEHICLE, THE SYSTEM WILL FAIL. Consequence:
IF THE OPERATOR PARKS THE VEHICLE, APPLIES THE PARKING BRAKE WITH THE FAILED AUTO APPLY PARKING BRAKE SYSTEM, THE PARKING BRAKES WILL NOT SET AND THE VEHICLE CAN ROLL INADVERTENTLY. Remedy:
DEALERS WILL UPDATE THE COMPONENTS OF THE AUTO APPLY PARKING BRAKE SYSTEM, BLEED THE HYDRAULIC POWER SYSTEM, AND ADJUST THE PARKING BRAKE. Notes:
SYSTEM: PARKING BRAKE.VEHICLE DESCRIPTION: MOTORHOME CHASSIS. NOTE: IF THE VEHICLE IS PRESENTED TO AN AUTHORIZED DEALER ON AN AGREED UPON SERVICE DATE AND THE REMEDY IS NOT PROVIDED FREE OF CHARGE WITHIN A REASONABLE TIME OR THE REMEDY DOES NOT CORRECT THE DEFECT, PLEASE CONTACT CHEVROLET AT 1-800-222-1020 OR GMC AT 1-313-456-4547. ALSO, CONTACT THE NATIONAL HIGHWAYT RAFFIC SAFETY ADMINISTRATION'S AUTO SAFETY HOTLINE AT 1-800-424-9393.
Actually, this more interesting than my day job right now. I've been studying these diagrams for the last half hour or so.
Tying port B directly to #4 might work. It looks like it should. You'll need to remove port F to #6 and cap that fitting, I think.
If those diagrams are accurate, and there's not more going on inside HR-1 than it appears, then all you're doing is taking the shift actuator out of the picture, telling it to ignore what the transmission is doing, and only pressurizing #4 when you want to, via the manual control valve.
Of course, all of this will only solve your problem if it really is the shift actuator valve that's the culprit. But if you've got a failing HR-1 or pump or something, this will at least simplify things and help you pinpoint the trouble spot.
BTW, did you also review the Dealer Service Bulletins in the back of the manual? Number 90-391-5 has diagnostic flowcharts and instructions for bleeding and replacing HR-1, number 91-240-5 discusses the auto apply valve brace, and 90-419-5 talks about a replacement hose assemply at the manual valve.
I do not believe that bypassing the shifter operated control valve will eliminate all the problems associated with the autopark. You still have the hydraulic system (mine is supplied by the power steering pump) to deal with. If the engine should quit while driving or the steering pump fails (in later models the separate electro-hydraulic pump), the spring/hydraulic application canister springs a leak or a leak appears anywhere in the system, the parking brake can self-apply while the vehicle is still in motion, it happened to me. Why GM in their infinite wisdom replaced the old virtually foolproof lever and cable system with this monstrosity is beyond comprehension. I fabricated a bracket that will allow me to mechanically release the parking brake if it ever happens again, fortunately I haven't had to use it (knock on wood). If it does happen again, guaranteed that the whole system will be scrapped in favor of the cable and lever. If your model is equipped with a foot pedal that operates a separate cable to the park brake, you can remove the auto cable and just use the pedal. Strangely enough, the transmission in my P-30 is equipped with a parking pawl (not supposed to be there)so I do have a back-up to take the place of the park brake. Hope you find this info useful.