Look what my coach has...What the heck is it?

[Petervs]

Hello all. While doing some chassis maintenance I discovered some hardware that has baffled me as to what it is, what it does, why I should be proud to have it, and does it require any periodic maintenance. And should other POGgers be jealous if they do not have them?

Pictures below. The items in question are two cylinders, about 4 inches in diameter and 14 inches high. Mounted vertically between the frame and the drive axle assembly just inside the brake cans, one on each side. There are two 1/4 inch hoses connected to a fitting on the bottom, and a 1/2 inch, thick walled hose connected to the top side of each one. They look like air hoses. The brackets these cylinders are mounted on look like they were welded in place by Prevost when the coach was built. You can see the cylinders at the 10 o'clock position of the drive axle.

The bottom has a rubber boot, underneath is a chromed 3/4 inch rod. The whole thing looks like an air adjustable shock absorber like we all used in the 1970's. I have not traced the hoses, they all go into bundles and are hard to trace. No mention of any of this in my Prevost parts or service manual, nor the Marathon paperwork.

Maybe this is some kind of perpetual motion air pump device that extracts energy from bumps in the road and adds the energy to the Detroit Diesel output?

Looking forward to reading your thoughts!

[dalej]

Peter,

I'm just going to guess on this one. When you raise you tag, these two cylinders help the four air bags so you coach doesn't drop.

I would think that if I'm on the right track, you'll be glad you have this feature since you hang a smart car on the back.

[garyde]

I remember a thread regarding this option. Like Dale has said, it is a lift. I don't know if its automatic but it is supposed to help when the tag is up.

[Jon Wehrenberg]

This is the hydraulic system that is activated by a switch up front when the steering wheel is turned to the extreme left or right.

There was great debate about this because Hector also has the system and instead of repairing it Prevost wanted to remove it. Marathon is said to have disabled the system on coaches that have it.

When the 45 foot coaches were first produced MCI for example had a steerable tag. That was the MCI answer to side scuffing of the tag tires. Prevost went another route. Their way to minimize side scuffing was to dump tag axle air. But they knew if they did that, they would in essence transfer 5 ton or more onto the four drive axle air bags and the rear would sag until sufficient air pressure built up to restore the rear to ride height. That was not acceptable so at the same time air in the tag axle air bags is dumped, a lever actuated switch located in the front compartment behind the bumper actuates the system to put hydraulic pressure on the devices shown. They look like shock absorbers and are in a way. They are called stabilizators by Prevost and they provide the support to the rear of the bus to compensate for the loss of support when the tag axle air bags dump air when turning.

I have them on my coach, Roger has them, Hector has them and there mayh be others. Prevost has discontinued their use.