[Larry & Diane]

The first place I would look is the u-joints. Try twisting the driveshaft foward and reverse with your hand. There shouldn’t be any slack.

[Peter]

Ditto on checking the U-joints, that would be the first place I would look.

[Archived]

Thanks so much, I will get the guys to start there!

[Archived]

One thing new owners have working against them is lack of experience with how a coach “feels”, drives, handles, stops, and sounds.

Before chasing problems there are a few things you might want to consider. See if you can hookup with another member near your location so you can compare coaches (kind of like you show me yours and I will show you mine) or have someone with experience driving a 2 stroke coach who can tell you if you might have a problem.

Vibrations have driven owners crazy over the years and they can be anything from nothing to a serious mechanical problem. Don’t rule out a tire issue, a driveshaft issue as has been suggested or a multitude of other smaller problems.

[Dick]

Please don’t crawl under the coach without heavy duty jackstands or heavy wooden blocks. You can never trust the air to keep the bus up. If the coach comes down, there isn’t enough room for you. Stay safe.

[michael]

A smart phone can sometimes be used to track down vibrations. Download one of the vibration analyzer apps, I use “FFT Vibration Analyzer” on my Android. This tool will give you a graph of vibration frequencies versus amplitude. Our tires rotate at approximately 500 rotations per minute at 60 mph, or 8 Hz. Assuming a sixth gear ratio of 0.639 and a final drive of 4.56, we can calculate the following approximate fundamental frequecies for tire, driveshaft, and engine vibrations at 60 mph:

Tire: 8 Hz

Drive Shaft: 8 (tire Hz) * 4.56 (final drive ratio) = 36 Hz

S60 Engine: 1450 (engine rpm) / 60 / 2 * 6 (number of cylinders) = 72 Hz

8V Engine: 1450 (engine rpm) / 60 * 8 (number of cylinders) = 190 Hz

Of course it’s not as simple as it sounds because each of the vibration sources will generate harmonics at multiples of their fundamental frequencies; however, the fundamental is the highest amplitude.

Jon, with his 1980’s rotary phone may be challenged in this area! LOL 🙂

[AL]

One simple area that is overlooked is if you have bad shocks it is not uncommon to get a feel as though something such as a tire or driveshaft is out of balance.

[Archived]

I love David’s assessment of things from a really technical standpoint, I read several times and then can be heard mumbling, what?

Keep em coming David…….

[Archived]

Tom, Be careful what you ask for! Ha! 🙂

The first six vibration modes of the Prevost chassis are probably in the 20 to 25 Hz range. This means that we’re not likely to feel normal engine vibrations during highway cruising, but we will feel driveline and tire vibrations thru the chassis. As Jon points out the trick is knowing what’s normal and what isn’t. My first impression of my H3 after driving it 4000 miles from Kamloops BC, as compared to my old Wanderlodge LXi, is that the H3 is much ringier. (If that’s a word). It’s like a tuning fork. The H3’s welded closed section frame members along with its adhesive attached composite exterior panels is stiff and lightly damped; as such, I do detect more transmission of driveline vibrations to the driver than what I’m used to. This is the price we pay for a responsive, well behaved, driving experience! It’s perfect! 🙂

[Archived]

David,

That was a word I was looking for. Ringier.

My 97 had 315 tires all around. when it hit certain types of bumps such as an expansion joint there was a thump as expected.

When I got the 06 with 365 tires, the same type of bump was less of a thump and more of a ringier or hollow sound. The noise level over bumps was a definite increase although on the plus side the coach does track far better than the previous 2 and is less sensitive to passing large vehicles where steering corrections might be required.