Hop or bounce in drive train?

[LarryB]

I am moving this question from an other area and asking it in a different way for hopefully more input.

I have had all 8 tires re-balanced and one re-placed due to out of round. I still have a hop,bobble,bounce at 58-62mph. I have had a slight problem since traveling South, but thought it to be a slightly out of balanced tire, something I could live with until I returned to Eugene.
After being parked 3 weeks the problem has intensified to a point something is required to solve the problem NOW.

All ideas welcome, I want to solve the problem before traveling farther as I don't know if damage is being done and I'm in an area [Phoenix] where I do have a few resources.

OBTW , I feel it in the seat of my pants, not the steering wheel.

Thanks

[JIM CHALOUPKA]

Larry, where are you with the shocks. Have you changed them lately. Might be as simple as the mounting bushings.

JIM

[hhoppe]

Larry: I'm sorry to hear you are still having problems. Have you talked with Prevost factory personell in Quebec. They would apt to have more answers to that kind of problem. I guess they had all of your tires and wheels off and balanced them. I don't recall your mileage. It is possible some driveline damage could be causing the problem. With all the aligators along the road (truck tire re-caps) these can cause real damage if kicked up under our coaches. I hope other Poggers weigh in here with more insight to your problem.

[ajducote]

Pure guess work on my part:
1. Check all lugs nuts to be sure they are tight
2. Check rims for damage / cracks
3. Drive shaft damage / bent
4. Drive shaft u-joints worn / need grease
5. Rock caught between the rear duals
6. Broken shock

[LarryB]

Jim, Harry, Andre, thanks for the input. The shocks are recently replaced. All tires balanced and a 3 axle alinement done 2 months ago. I don't recall hitting anything in the road.

I have a call in to Bill Jensen @ Prevost. Like to find a Prevost service center here in the Phoenix area. I'm calling Desert West Coach this AM. Maybe they can get under the bus for a "general condition" look.

[sawdust_128]

Do you feel it at 58 - 62 mph or does it only occur between those speeds?

Also, did I read that right, did you say the this problem became worse while the coach was stationary for three weeks?

[Jon Wehrenberg]

If you know the tire/rim combination is not out of round and is balanced it could be the driveshaft.

When this occurs are you coasting, accelerating or maintaining speed under load?

BTW, if tire balancing was done with weights instead of Equal or Centrimatics are you sure they are still in balance? Jim Keller had a demonstration proving his tires rotated on the wheels after being installed under heavy braking so do not assume because someone added weights that the balance has been maintained.

[Kenneth Brewer]

What Jon said about bead slippage/relocation can be confirmed by my experience. Failing that, what you've described, if I think I understand & convert your words to how I might describe this problem, it might be either or both of the following cases I encountered on the Bluebird FC.

1. The inner and outer rims on the drive axle are not aligned. In other words; in relation to each other, wheels have shifted off center. I loosened and then tightened both the inner and outer wheel lug bolts & nuts (Budd wheels here too) and found it had a huge effect on the vibration.

2. But it kept happening even when I overtightened to keep things from moving. Then in a flash of brilliance (or old age experience), I decided the same thing, perhaps, had happened back in '67 when I bought a '63(?) Olds 98 and the wheel bearing were bad. I pulled the axles on the Bluebird and then the wheel bearings and both races were scored and and roller cages were so worn that the rollers could turn (skid). Replaced them and the problem was solved.

The thing here though is that your coach is essentially new (2000) and it seems unlikely unless lubrication (low or improper HP gear oil) killed the bearings.

But you might try making sure the duals are centered up first. If they are semi-loose somehow they can do what it seems you are describing.

[flyu2there]

Larry,

Desert West is your best resource, not nearly as "pretty" as Prevost but they know their onions. I am gone to make a small wager that it is a U Joint n the process of flying West!

John

[Jon Wehrenberg]

That would be my second guess as I mentioned above John, but if the balancing was done via weights the tires could be out of balance and more likely the cause. U-joints typically start exhibiting that clanging noise when going in gear or when shifting between drive and reverse.

Also, flat spotting from sitting is something we all have to recognize. I ignore how my coach feels until I have been at highway speeds for about an hour.