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Drive axle shocks
I am in the process of replacing all shocks,airbags, norgren valves and anything on the suspension thats looks like it could be original equipment or worn. Ordered all parts from Prevost to make sure I got the correct parts for this bus shell. All went well on the front. Replaced all Norgrens,shocks,airbags,ride height valve and the level low manifold assy.with new solenoids. Airbags are dated july 1993. Bus is a 1993 shell.
Started the rear and discovered the shocks are not the same on the drive axle. The front two shocks on the drive axle are air shocks. The 4 shocks I ordered from Prevost and are supposed to be correct for this bus. The shocks have a large airline going into the top of the shock and two 1/4″ lines going into the side. They appear to be original equipment and are junk. The bushings are completely gone. The smaller airlines appear to be plumbed into the 2 pos norgrens on each side.
Has anyone encountered these type shocks ? Could they have been an option? I have not received the new shocks from Prevost yet however I know the 4 drive axle shocks are all the same P/N.
Any thoughts?
Michael
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4 Replies
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They aren’t shocks. They are part of a system called a stabilizator, no longer available that was used to keep the tail of the coach from dropping when the tag axle is lifted.
I don’t know this to be fact, but some converters, (Marathon possibly) would disable the system. I don’t know why because I had it on my 97 in conjunction with the automatic tag axle air dump when the steering wheel was turned to the extreme left or right and it kep the tail from dragging by hydraulicaly supporting it when the tag axle wasn’t contributing to supporting the rear.
I know of at least 3 coaches that have the system in addition to yours.
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Jon,
I am really confused now. Just when I think I have this thing mastered I run across something unique or different !
Did these come from Prevost or are they aftermarket? They appear to be OEM. Its apparent that they are in bad condition, bushings gone on both ends and leaking. It sounds like a nice option to have. Since they mount on the shock mounts do they act as a shock when not activated ? Are they still available ? Expensive ? Would you replace them or block them off and install regular shocks. Any input is always appreciated. thanks in advance
Michael -
Jon,
May have answered my own question. The stabilators are still available although are cost prohibitive. Over $1K each. Prevost says the original bushings were a hard plastic and with age would somtimes shatter and fall out. The new bushings are poyurethane and should correct that problem. I did not realize they were actually Hydraulic cylinders. Assumed they were air operated. I traced the large inlet line to what appears to be an electric hydraulic pump mounted on the bulkhead in front of the drive axle. Still not sure how they get activated as the air lines on the bottom go to the 3 ports. Triggered by the tag axle raise valve?
At any rate, am going to replace the bushings and see what happens. Given they are hydraulic, I am not surprised to see them damp/wet on the cylinder end. I am assuming that if I unplug the electrical connection at the pump it would disarm the function if needed. Does my train of thought sound reasonable ? Thanks
Michael -
First, they are rebuildable if you want to go to the effort. A member rebuilt his system with great results. That should change the economics.
It is an air over hydraulic system so there is no pump involved, but it has electrical controls that may or may not be connected or functioning. It starts with a “cam” at the steering arm which actuates a switch when the steering wheel is turned full travel in either direction. That actuates the hydraulic system while automatically dumping air from the tag axle air bags. Its purpose was to stop the side scuffing of tag axle tires when a sharp turn was required automatically. I no longer have my coach that had the system so I cannot get more specific. If I recall the shop manual section covering that system was kind of limited.
I replaced the bushings in mine with the black hard rubber ones. In fact I am using them on all places the red polyurethane bushings are used because I have seen the red ones fail catastrophically. Once they start to go bad it only takes a few hundred miles to go from no evidence of failure to totally gone. The rubber ones show signs of failure long before they disappear making routine inspection and repair easier. When the bushings are gone the noise from the clanging parts is loud.
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