[Don]

Check the “sway bar” bushings. Shocks might be OK and their bushings are shot. You may have one or more shock end broken off, causing the shock to bang around. The adjusting bars holding the rear axle in proper alignment might be loose. If you have stabilizator hydraulic supports, their bushings are likely to be missing or shot. Your trans retarder accumulator attachment bracket might be broken. Due to your coach weight you are obligated to use a very high tire pressure. Your king pin bushings might be shot. Your muffler might be loose.

These are things that I can easily think of that might make suspension noises. Some very likely and others not likely at all. Get it up on a lift and look around they will all be easy to spot.

Pay someone for lift or pit time or go to prevost for an oil change and they will find all above items are good or not in the process. Shouldn’t be any extra charge if you don’t want defects recrified.

If you have IFS you may need bushings there.

JIM

[Archived]

all of the previously mentioned items are valid, however, I had my coach a long time before I realized that the front mud flaps would drag on the ground on certain types of bumps.

[Gerald]

Pretty sure they were the original shocks. No more wallowing in road dips. Definitely a worthwhile improvement.

The coach rides well on the highway but I still hear some groaning in front when the suspension flexes on secondary roads or in town. Sounds like it is coming from the air bags but I doubt that they make a noise. The air bags look fine. I looked at the sway bar bushings and they look perfect. Mud flaps are ok. The suspension parts seem well lubed. What should I be looking at next?

Do I have unrealistic expectations? Will there always be some suspension noise?

[Archived]

On mine the chrome piece under and behind the ft bumper has viberated at different speeds sounding as if i had bearing trouble . ill fix it and it will come back just a thought for you .

[Archived]

Gerald,

Trying to diagnose the origin of sounds is difficult if not impossible when in the coach. Giving a good diagnosis on a forum borders on insanity. Believing what we tell you is even crazier.

But what the hell. If we weren’t crazy we wouldn’t even own buses. If you get under your coach, especially since yours is an IFS coach you will note a lot of bushings as part of the suspension. The major suspension members are not rotating around a bearing, but have a flexible bushing that allows movement. Every coach I have owned which includes two solid axle and my current IFS steer axle make noises. Due to my driveway slope and the manner in which I have to raise and lower my coach to get it into the garage I have an opportunity to hear the coach creak and groan as I raise and lower it. Going from completely lowered to fully raised my coach makes noises. Then as I go down the driveway at idle, in neutral, while the coach is going to its driving height I hear more noises ranging from creaking to popping. I also hear the flaps drag so I am acutely aware of all the sounds just to get out of my garage to the bottom of the driveway. I suspect the sounds you hear are normal, but until you can get comfortable with that opinion it would not hurt to have someone who knows Prevost coaches look it over. The IFS has for some owners been an issue, and some have replaced bushings.

Jim mentions bushings and the red urethane bushings in sway bar links for example seem prone to failure. but having had the pleasure of driving with a failed bushing the noise is a distinct clanging which leaves no doubt there is a problem. As a note, when a red urethane bushing begins to fail you see chunks of it coming from its location, and it goes from starting to fail to total failure in a relatively short time so at every oil change I make it a point to give the bushings in my coaches a good inspection. Had you mentioned a banging or clanging sound I would steer you towards bushing failure, but I think you are experiencing normal sounds. But don’t accept that opinion unless or until you have someone verify it. If I lived near you I would suggest just taking your coach for a short drive just to see if the sounds are what I was used to. For the short term if you can hook up with someone who has a lot of Prevost driving experience you might be able to get an idea if the sounds are normal or require some checking.

[Archived]

The front end of my 99/98 creaks as well when going over bumps, especially when just starting a drive for the day. This was driving me nuts. I too assumed shocks and had them replaced. I now have new front shocks AND the creaking sound. I had not Prevost shops tell me it was upper bushing pointing out some rubber failure. Bill Jensen of Prevost said that the failure of the outer part of the bushing was not necessarily an indication of bushing failure. I took the coach to Prevost Ft Worrth and they confirmed that the bushings were good and that all other front suspension components were good, except the blown or missing dust boots. They suggested I do nothing. I asked if spraying the dry bushings with dry silcone would be worth trying. They said it might work, but may not get far enough into the joint to stop the creak. Again, they said they would do nothing.

[Ed]

Jon and Gil,

Thanks for your comments. I suspect you are correct and these are just normal noises driving a 50klb vehicle over anything but perfect roads. I’ll focus my attention on other things such as OTR and Techlink. Good thing I enjoy researching and fixing things.

[Ace]

I don’t think an awareness of noises is a bad thing. The problem is learning what noises are normal and tuning them out so you hear the ones that are an indication something needs attention.

Gill made an excellent point that is worth keeping in mind. The bushings in the front suspension may look bad, but as Bill and the folks in Ft Worth point out the appearance is not how a bad bushing is determined. If the pin going through the bushing is loose then the bushing has failed. Not until.

[Dale]

When I bought the 99 bus that Gil now has, the dust covers were deteriorated, but the previous owner had the front end checked at Ft Worth and they said there were no problems. It did groan then, probably the same as now. I heard a rattle when I got the bus home for the first time, and found the red/orange bushings were completely shot. It was an easy and inexpensive fix. Jim Keller was told that these bushings need to be replaced about every 60K miles. I think the bus bodies are like ours, the older they get , the more they groan even if nothing is seriously wrong.

[Harry]

Sorry for resurrecting this old post. I recently experienced the exact symptoms as Gerald. It would only happen at city speeds when the bus would propose over bumps. I finally realized what was happening. Because I was driving slow my foot was barely engaging the throttle. When I hit a bump my foot would momentarily go to zero throttle allowing the Jake to cycle a couple of times. Jeff just installed new front shocks so I no longer experience the proposing. This drove me nuts for a while before figuring it out. Again, sorry for digging up bones but didn’t see a resolution and thought it might help someone else with a Jake and a bouncy classic. Just trying to fill in the database.

Gerald,do your remember what was causing the noise? Jeff

[Archived]

Jeff, your throttle should have a time delay built in to minimize or prevent situations you describe. I just cannot remember if it was a DDEC function or was built into the TPS.

[Archived]

Jon, that’s interesting. There does seem to be a 1/2 second or less delay for the Jake’s to engage. It was actually almost impossible to duplicate driving on flat and feathering the throttle. Now I know why. There seemed to be a cumulative effect of crossing the fuel no fuel positions quickly maybe 2 or 3 times on bumps. I could not duplicate with my slow foot and ankle dexterity. In any case the symptom went away after I turned the jake off or made a concerted effort not to go to zero throttle. Since the front shock replacement it doesn’t do it at all. The shocks were really bad and I didnt realize how much the front was moving. If I can get the old ones back from Jeff we could have him slap them on Tom’s coach to see if we can duplicate it. On second thought from reading other posts they may already be on there. Thanks for bringing that design nuance to my attention and keeping my post from possibly leading someone else down the wrong path.

To be open to possibilities it may have actually been the shocks themselves. However I was pretty sure it was the Jake’s cycling.

[Archived]

wow. This place is rubbing off on me. You guys have me picking on Tom and I have never even had the pleasure of meeting him.

[Eric]

Be careful, he is the guy that will double your dues at the mere mention of slides.

[Jerry]

I got my eye on you Rosco…..