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.

[JIM CHALOUPKA]

This is a real long shot, but could there be something going on with the toad.

Drive around the block without it.

JIM

[Orren Zook]

Larry,

I'd bet your problem is a balance issue if it comes in and then disappears at a certain speed each time. When you had your tires balanced were they spun or static balanced? If you use equal or dynabeads in your tires or balance masters / centramatic balancers they are not compatible with lead weights.

[rfoster]

If you had your tires balanced with lead weights, you will need to have equal or similar product installed.

Jim Keller proved to us in Branson that wheel weights on the Prevost rims are a waste of your money. The tire will slip or slide on the wheel under heavy braking - eliminating the supposedly fix by installing weights on the rims. If you really want to go the xtra mile, add centramatics wheel balancers.

If you still have reservations about this, have your wheels balanced and mark on the tires with a chalk line were the weights are positioned then drive the bus and hit the brakes a few times some what severly and the tire will slip.

Hope this helps and good luck.

[rfoster]

I went back and read some of the previous post and see that Jon has already posted about the wheel weights issue.

Never mind.

[LarryB]

Thanks All for the input.

What I did today, all 8 spin balanced, nothing added only lead. [no heavy braking] problem seem to only slighty changed to smoother.

One tire out of round, one alum. wheel both replaced, problem still there.

What I have noticed, as Jon asked the problem seems to be consistent coasting but seems also to increase adding throttle. I think I notice a slight increase if a jarring bump is hit.

Having ride height and u-joints and general condition inspected in the AM.

Will post findings. Thanks again,

[Joe Cannarozzi]

Lets see if I can guess what brand of tires you have. Could it be the ones that they charge double+ for because they are labeled with the preferred brand.

Sounds to me like a tire is separating.

If you have a 40 you can get the tag up and see if there is any difference and with no shimmy on the steering wheel that would narrow it down to the drives.

The drive shafts are so short it would be pretty obvious if something were out of whack there.

[JIM KELLER]

After reading these posts I'll go on record placing my bet on damaged or bruised belts in a tire as a result of rubbing a curb. [ No disrespect for your driving abilities, just a common problem. ]

[LarryB]

Jim, no change Toad or no Toad.

Jim K. The tires are new and no curbs hit yet. I know the time will come for curb contact so no offence taken.

Joe, I have Michelin XZA1 315. 2 months old with 2000 miles. I have a 45, and to be clear I do not have steering wheel shimmy, just a general hop, bounce,bobble. It won't spill my coffee but it sure is a PITA

[JIM CHALOUPKA]

Larry, did you have this sensation befor the new tires?

If not I would suspect the tires. Good luck with that!

JIM

[LarryB]

OK, Here is the answer to the bobble/bounce.

I had the ride height checked, left side 1 1/4" lower than the right.
Corrected.
The rear engine mounts were loose. Corrected
The tranny end of the drive shaft 'U' joint was worn out. Correct

The test drive was great, no more B&B thankfully.

Thanks again to all that offered up ideas, since ultimately everything that was suggested was done, you were all correct.

I have another problem to discuss, but I'll yield some band width to someone else for now.

Thanks again to All.

[flyu2there]

"OK, Here is the answer to the bobble/bounce.

I had the ride height checked, left side 1 1/4" lower than the right.
Corrected.
The rear engine mounts were loose. Corrected
The tranny end of the drive shaft 'U' joint was worn out."

Jon,

Eat your heart out! Motor mounts..won't make it shake, ride height, no factor, but U -Joints... Bingo

Glad you got it fixed Larry, hope Desert West (if you went there) did well by you!

John

[Joe Cannarozzi]

You know how long you have to go without greasing or inspecting a U-joint to get it to the point that it wears out I do.

20 or 30 thousand miles. What else or what next that would be my question.

[JIM CHALOUPKA]

Yah, and be checking for leaks at the transmission output shaft.

JIM

[LarryB]

Joe and Jim I guess you are correct, but my immediate question is why the 'Honyak' that lubed the bus 2000 miles ago didn't find the sloppy 'u' joint. When inspected,[torn apart after removal] there was plenty of grease in the 'u' joint.

John, I didn't go to Desert West, I couldn't get them to call me back on a wheel I needed, so I ,in a pissy mood, elected to go to All Aborad America's shop in Mesa. Great group of guys, Leo the service mgr. is a good guy as well, got me in and on the road in short order.
They run a fleet of 40 or so buses plus service several motorhome & entertainer buses. I would recommend them highly.

[Joe Cannarozzi]

He was greasing it with his eyes closed.

Coveralls and a grease gun. Best fifty bucks you will ever spend. Do that yourself. I find something new, wrong, almost every time I grease:)

Larry what Jim was eluding to in his last post was a u-joint that far gone and out of balance puts a great amount of abnormal stress on that trans seal and pinion seal the 2 yokes they ride on. They could have been damaged as a result.

In defence of the previous owner that u-joint may have been either defective or installed incorrectly.

[Jon Wehrenberg]

I don't think the guy 2000 miles ago would have known unless he was looking.

I haven't had a U-joint failure on the bus but over the years with Corvettes and rear independent suspension I got to see and replace many defective ones. The first sign is that dry reddish powder. It is usually only at one cup. Our buses call for lubrication every 6000 miles or so. How many coaches only get lubed when the oil is changed, and how many oil change intervals are stretched to 20,000 miles? Grease is cheap.

If the U-joint has a grease fitting (factory originals on the Corvette did not) it is because the grease passage to the bearing cup was blocked that a failure occurs prematurely on joints regularly greased. Our buses have two grease fittings 180 degrees opposed. I give each a shot and make sure I see evidence of grease at each cup. So far, so good.

[LarryB]

Well, Hate to tell you all this BUT_____ the bounce is back.

We were on the road this AM headed North and at higher speeds than I normally drive 67-72 mph the bounce is pronounced. At 60mph the bounce is very slight [gone at 62-64 range]. I had a chance to experiment with speeds and different road surfaces and this is the condition I have now. Strange that the problem is less and has move to a different speed range. Before you ask, the test drive was done in Phoenix traffic so I guess not a real test drive.

I plan to press on toward home avoiding the speed ranges were the problem occurs and attack it again once home.

It has been suggested to have the engine tuned and the tires trued, would either of these contribute to the problem.

[Joe Cannarozzi]

Sounds like you may still have a drive shaft issue. The yoke could be wore out, it happens, that possibly may be the cause of the joint failure. It could be loose pinion or outputshaft nuts, the shaft may be bent from a foreign object, a balance weight may have flown off, the slip spline may be bad. You may have damaged other things as Jim said. A bad seal will not make you wobble but the bearings in the trans tail shaft and pinion bearings in the rear-end could have been hurt as well as the other u-joint could have been hurt from that first failure.

I would concentrate there.

Could be the new joint getting destroyed again already . It may be when you thought you found the problem you may have just fixed the resulting damage there of.

To add to Jons comments when you are greasing that you should make sure that you see new grease at every cup, it should appear at all of them at close to the same time. If you see one of them doesn't bleed grease till way late that is the beginning of the end. Grab the larger diameter end of the shaft (in the middle), at the spline, and jiggle it to check for excessive slop, should be minimal. Grab each yoke one at a time and do the same there should be almost no slop there. Check slop two ways there up and down (bearing) AND clockwise/ counterclockwise (u-joint).

[JIM CHALOUPKA]

Larry, look into changing the universal joint at the other end of the drive shaft.

Maybe you did, if not you should have.

Have the bearing and seal at the output shaft of the transmission checked. The bad universal that you replaces probably damaged it. IMHO if you need that bearing I would only have an Allison repair facility do the work.

How many miles on your bus? I think many here want to know.

It is possible that the drive shaft is not running true (maybe never did when new) and/or is out of balance.

Balance Master Co., makes a split collar balancer for the drive shaft.

JIM

[flyu2there]

Larry,

Glad to hear that you got everything fixed. Remember the addage from flying, if it ain't broke, don't fix it!

I will score those peoples name, Desert West has been good however it is in the shi%@r part of Phoenix and you really do not want to be there after dark. Wayne Mullis made the offer several times, spend the night...No Thank You! Too many run by fruitings in that hood...............

Run the coach for a while before you do anything, IMHOP


Best,

John

[Kenneth Brewer]

"Well, Hate to tell you all this BUT_____ the bounce is back."

Sorry to hear that.

I'll just wait with interest, but as I said, I think I had the same problem, just not on the Prevost.

[flyu2there]

Well, Hate to tell you all this BUT_____ the bounce is back.

We were on the road this AM headed North and at higher speeds than I normally drive 67-72 mph the bounce is pronounced. At 60mph the bounce is very slight [gone at 62-64 range]. I had a chance to experiment with speeds and different road surfaces and this is the condition I have now. Strange that the problem is less and has move to a different speed range. Before you ask, the test drive was done in Phoenix traffic so I guess not a real test drive.

I plan to press on toward home avoiding the speed ranges were the problem occurs and attack it again once home.

It has been suggested to have the engine tuned and the tires trued, would either of these contribute to the problem.

Oouch Larry,

Jon never exceeds 62 mph so you could go with his theory. I'm like a 75-80 mph person so that won't float. Head over to Desert West before you leave, ask for Wayne thence proceed to puke in his Wheaties...POG Member yada, yada, yada. His service manager is from Marathon, married some chick who refused to live in the Beaver state (I understand).

He will find it and fix it...no choices on this one if it has re-appeared.

John

[Jon Wehrenberg]

I have been known on occasion to slightly exceed 62.5 MPH. So I feel fairly comfortable saying if Larry is still experiencing a vibration, he should note all of the specifics.

Was he coasting, accelerating or maintaining speed under power. Is the road a contributing factor There is a three mile section near my house where I get a vibration in every vehicle I own like a tire is out of round or balance. It has to be the road surface.

Replacing a U-joint is something that has to be done correctly. If it not exactly centered in the drive shaft or yoke it will create a vibration. The fact that something changed when the U-joint was replaced keeps leading me back there.

Joe is correct. The driveshaft can be out of balance, or there could be slop in the spline. Unless someone monkeyed with the tires as well as the u-joint concentrate on the driveshaft from transmission to differential.

[LarryB]

Jon, as to specifics ; the problem happens while coasting, accelerating,or maintaining speed. Road condition, the smoother the road the more noticable the bounce.
The 'U' joint was replace by a qualified shop with qualified techs, but someone may have screwed up--sure, I doubt it. The new part may be defective as well.
No one "monkeyed" with the tires, I was with the bus the entire time. I didn't drop off the bus and go to diner.

John, Desert West is in my rearview mirrors. We are in Camp Verde north bound. As I said --if they can't return a phone call that will result in the sale of a new polished alum. wheel, I'm not going to give them my business. In today's economy, they better get their s--t together or we will be lamenting another RV store shutting the doors. Just my opinion.

[Jon Wehrenberg]

Larry,

The fact only the U-joint was changed, and that changed the speed of the vibration event strongly suggest the issue is somewhere in that driveshaft. Balance, U-joint off center, something.

[LarryB]

Jon, going on that assumption, driveshaft, if I avoid the speeds that the vibration is most pronounanced, in your opinion is it safe to drive another 1000 or so miles home?

Thanks

[gmcbuffalo]

Larry at the nearest large town stop and look up a driveline shop and have them spin your driveline. Most big shops work on trucks and cars so they should knew how to handle your bus. A clearance from them should eliminate anything to do with your driveline or u-joints.
GregM

[LarryB]

Greg, thanks, we will be in a few larger towns before we get home. I'll check it out.

[jimshoen]

Larry,
Sorry to hear DWC did not return your call promptly. I know the owner and the manager at DWC and it does not sound like them not to be in touch with you. If you ever call them again, ask to speak with Chris Weaver, manager.
I have been satisfied with the work they have done for me over the last two years.

[Jon Wehrenberg]

Larry, I would drive it home and keep away from the speeds which create vibrations.

I know from testing on products we used to make in the factory that the right vibrations can disassemble anything. That is not an exageration, but a statement of fact. We built shipping skids for Cummins engine and they had to undergo severe testing because they were to be returnable and have a 20 year life while enduring all modes of transportation from ships to planes to railroad to truck.

During the testing process I watched the vibrations at one phase of the cycle unscrew the bolts in the engine which was secured to the skid.

[LarryB]

Jon, thanks for the info, I may just press on home and get the Bus into a shop when I have time to sort things out and not be in the travel mode.

Jim, DWC did not return my call at all, Never heard from them--go figure. Cost them the price of a wheel and a service call, and I suppose, me as a customer.

[flyu2there]

Larry,

I too am sorry to hear about DWC, maybe they have something going on there, who knows?

Your the PIC however I would have some concern about trying to limp the coach back North, at least too far. Have to ask yourself about the driveshaft, they don't just start wobbling unless they have been damaged and I doubt that happened on your watch. Every u-joint that I have had fail has given pleanty of notice, usually a nice clunk when you put the vehicle in gear or shift from forward to reverse. You might ask someone to stand outside the coach an have a listen as you move it from D to R a couple of times. Maybe, just maybe, you got a bad u-joint at replacement. Doubt it is the tailshaft in the transmission because it would spew ATF long before you could feel it. An internal problem in the transmixer would probably manifest itself also with high oil temperature. Doubt it is a wheel problem because you would be getting some kind of funky tire wear in just a few miles. Certainly not a wheel bearing which comes down to maybe a dragging brake or pehaps a spastic air bag...but that would be a real reach. Keep us appraised...


John

[ajducote]

maybe I missed it, but was this problem ever completely solved?

just wondering???

[LarryB]

Andre & Ann, I am remiss in not reporting back on my problem.

I nursed the bus home driving at speeds that the 'bounce' was at it's least. I have an appointment at an alinement shop in a few weeks to start the troubleshooting process.

I will report what is found and the results.

Larry

[Jon Wehrenberg]

I'm really curious to learn how a shop can think alignment will cure a condition that sounds like an out of balance situation on something that is rotating. I'm even more curious to learn how they can find the problem without burning through your money as they try out different things.

If you are like me they will have the entire bus balanced before they find something simple like a loose axle bearing nut.

[LarryB]

Jon, since you are probably not familiar with some of the shops in the RV Mecca of the greater Eugene, OR. area, you may not be familiar with Kaizer Brake and Alignment. They are the shop Marathon sends their Buses too. They can deal with drive shaft, brake, tire trueing, as well as most all suspension issues. They were the folks that did the alignment, brake work, as well as axle bearings on my Bus prior to delivery. I am expecting them to check their work and, stand behind it. They have in the past and I expect nothing less of them this time.
As I stated in a previous post, I am going to "start the troubleshooting process." It's the process of elimination, is it not.

[Jon Wehrenberg]

It indeed is the process of elimination. I just cannot imagine how they can simulate the speeds required in the shop to identify the situation leaving only trial and error as the means to eliminate possibilities one at a time.

If you never had the problem or if you had it, but it changed speeds all of my efforts would be on "what has changed?"

[hhoppe]

LarryB I'm sure glad to hear you got the coach back to the source of the problem. They should indeed find and fix the problem on their nickle. I sure hated to see you having so much trouble with a new to you unit. We enjoyed being your neighbor in Tucson and hope to meet again soon on the road.

[LarryB]

Jon, So how would you handle the problem? How would you simulate the speeds required?

------------

Harry, Teddy and I enjoyed our visit in Tucson as well, sorry we didn't have more time. Thanks for the tip on the Mex. food in Green Valley--it was great.
My problems will be solved, and we will be on the road again shortly. We are enjoying the Bus inspite of the 'bounce'. Almost everything is working as advertised. We expected a few 'worts' in a 10 year old bus, but I'll get those squared away.

[Jon Wehrenberg]

Larry,

That is the problem with the type of problem you describe.

If you have a vibration at a specific speed it is likely someting that goes around is out of balance or is loose. Loose can be any number of things from a set of lug nuts, to an axle bearing nut.

It could be something out of round, such as a tire, or something misaligned like the driveshaft due to a faulty U joint installation.

You mentioned once (I think) that it occurred at a certain speed and then some work was done and the speed it now happens has changed. For me that is an indicator that whatever was worked on in between the change in speeds is the focal point.

I also would not rule out a start from scratch. If you have wheel weights I would check each tire's balance, or get rid of the weight and use something like Equal, or Centrimatics.

I would not put the wheels on the ground after remounting unlit I had rotated the wheel and made sure it ran true. You could raise it off the floor and spin it to make sure there is no wobble or out of round situation. I would also do a very careful inspection of the tires because if the tread is beginning to separate that could be your entire problem.

Like finding air leaks there is no silver bullet. You just have to methodically do a check, starting with whatever was worked on that caused the change in speed, and just go through the entire coach. I would also rig a dial indicator up to the driveshaft, and check each end while rotating it.

Once you have balanced and checkd for out of round at every wheel and tire and the driveshaft I would pop the axles (takes about a minute) and verify the bearings are running quiet and the locking nuts are tight and secure.

Good luck.

[GDeen]

Been doing some reading on balancing Larry and wonder if the product on the following website might be worth trying. Different ways to center the wheels on the lugs including removable centering pins or attached sleeves.

Obviously nothing magic, in fact it is very intuitive and they seem to have a satisfied following of real people on their testimonial page. Sounds like several customers have gone through some of what you have and this cured their problem.

Cheapest looks to be "solution A" which is the 3 pin removable centering kit for mounting each wheel. Sounds like a reasonably inexpensive means to eliminate one potential variable.

http://www.tru-bal.com/index.cfm

[Jon Wehrenberg]

Just out of curiosity, when anyone has spent $6,000 for a set of new tires has anyone ever seen the wheels re-installed using these centering devices?

Conceptually it seems like a great idea to eliminate a potential vibration, but unlike nitrogen that the dealer can sell, it seems to me the dealer can't make a penny on the use of these devices so he just will not use them.

I can hear the conversation now: "Hey Mr. Prevost owner, now that you have spent mega bucks on tires and nitrogen, would you like to spend a few more and have us actually center the wheels when we install them, or would you rather we put them on off center? The cost is only $10 more per wheel."

If we think about this for a moment, our wheel mounting procedures calls for us to mount them and torque them to the Alcoa spec. Then we are to drive some distance which I think is around 500 miles and retorque them. I think that advice is because if they did not center during mounting initially, after driving a while they will center themselves which is why the retorquing is called for.

Not spoken is the fact that after mounting and tightening we can easily verify the wheel is centered. Lower the tire until it is barely touching the floor. Rotate the wheel. If it is not centered it will either scuff the floor, or the gap between the tire and floor will change. I have never seen anyone do that.

[truk4u]

If there was a benefit for the centering device, the trucking industry would be all over it. I have never seen one used. Joe?

[Orren Zook]

I noticed in the video that he 'torqued' the rims to specs with his 1" impact wrench ..... with hub piloted rims centering shouldn't be much of an issue.

[Kevin Erion]

I had to watch to make sure, these wheels are "hub" pilot wheels. The older trucks and buses, mine included have "ball and seat" style wheels, they center with the lug nuts so this application does not apply.

[Joe Cannarozzi]

Even with the old style non piloted hubs it would not be necessary. The tapered flange on the rims and nuts center things up.

Go with the centronics or the balance masters. I had never had them till I got the bus and they are a dream. Pricey and worth it. I have good test results that the balance masters that use mercury are better than centronic.

[GDeen]

Joe,

I don't know enough about the bus wheels or how they center or seat or whatever style to know if the product was applicable but it certainly made sense....

Actually found the Tru-Balance site as a "favorite link" from the Balance Masters site....occurred to me they may be related.

[Joe Cannarozzi]

On the new piloted hubs and the corresponding rims the clearance between the hub and the rim is practically zero. I do not know how it could be any truer. I believe it was the intent of the designers to do just that.

[LarryB]

Gordon, thanks for the info, I appreciate it.

[Orren Zook]

Another thing to check is whether your tires are actually out of round, some alignment and tire shops are able to 'true' your tires to a more perfect tire diameter, eliminating wheel hop from out of round tires. Also for those inclined to do some of their own tire work - here's a must have for your tool box: torque sticks! They will stop tightening when a maximum torque limit is reached.

http://www.asedeals.com/accutorq.html