Shock Bushings

[Jon Wehrenberg]

This comes under the "for what it is worth" department.

This week on a trip we heard a new noise in the rear while driving. It seemed like it was the shower door banging or something loose. After a while my wife found it coming from beneath the coach so I looked when I got it stopped.

Our coaches use a hard but flexible plastic bushing in the shocks and hydraulic cylinders (an option on 45 foot coaches with automatic tag axle unloading in the turns). As I found out on a car I have been maintaining the material is great right up until it starts to fail, and then in a very short period of time it fails catastrophically. Unlike the rubber bushings which tend to dry out and elongate the holes, but still remain, the plastic, which I think is polyurethane comes apart rapidly in chunks, and you have a shock (or radius rod bushing) banging metal to metal under the coach in your suspension.

I removed the shock with the failed bushing so the constant metal to metal banging would not destroy the mounting stud or the ring on our return home. I think the damage that could have occurred would be substantial because once the bushing failed and came apart in chunks, every slight variation in the road resulted in a loud banging noise.

The good news is that Prevost stocks these bushings in large quantities and they are only a few dollars, so if caught early their replacement is easy and cheap. If allowed to bang around a while the cost to repair the damage could even involve welding a new stud in place or replacing an entire shock absorber or hydraulic cylinder.

[ken&ellen]

Jon, Is this plastic piece also on the 40's ? Should this piece become part of the PM of the coach? I do not believe I have that auto feature on my Liberty.
Ken

[Jerry Winchester]

Liberty will be sending out a note shortly covering the issue surrounding a third order harmonic imbalance that is causing a high pitched (non-audible) pulsation in these shock bushings that when placed in the right configuration can lead to a temperature imbalance in the range of the autoignition temperatures of said bushing material.

The bulletin will recomend bushing replacement or the addition of a small dog in your coach as an early warning device.

[Jon Wehrenberg]

K&E,

Your coach will not have the bushing in the air over hydraulic cylinder I discussed, but you do have it in your shock absorbers and possibly suspension links.

Based on what I saw if everybody keeps an eye on the condition of the bushings on their shocks, suspension and stabilisators (I'm not making that up, that is a Prevost name for the things) you should have no problems, but at the first sign that the bushing material is starting to disintegrate or fail I would urge you get it repaired because those things went from bushings to pieces of plastic junk in a few hundred miles.

Ignore JDUB. He has a lesser coach and is envious.