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Vibration-Am I missing something?
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Jacking the engine & trans seams a bit scary, that’s a lot of weight concentrated on the pot metal cast oil pan. How much do I need to lift/jack the engine/trans to determine bad mounts?
I understand your concern with weight. You might try loading the bus weight by blocking your wheels, step on brake hard, engage transmission, increase throttle. Watch the engine for lifting or movement due to a failed mount. Drive and Reverse will load torque to observe failed mounts.
AL
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Tom;
At this point I could live with slight vibration, it’s definitely more than slight since the new 365s have been installed.
Mark:
Great question, I think the vibration is there both under power and coasting but I will make sure to pay close attention to that during the next drive.
Fujimo:
The bridge joints/pot holes where the small ones you run into ever day on the interstates. It has been suggested the slight jar when running over a bridge joint or perhaps dip in the road is a better description is better than pot hole would jar or dislodge the beads that were inside the tire at that time causing a vibration until the beads found their happy spot again. As to the looking under the coach, I have had both JoSam’s and Prevost Winter Garden do a thorough inspection of the undercarriage/suspension. They found no irregularities.
Al:
More good stuff – I will do the load test in F & R as you suggested. I am thinking I should also leave the parking brake on along with your other suggested safety items of blocking the wheels and stepping on the brakes hard. I believe the engine will lift a little even with new mounts, what is considered lifting to much?
Chuck
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I have found Road conditions play a Hugh part in vibration . So have you been on any road surface and experienced No Vibration ? If not then a visit to Prevost is needed . After all they made the coach 🙂 Happy New year Guys , may your repair cost be lower than mine lol as i sit and await the Genny motor rebuild 🙁
My saying is Smooth Road Smooth Ride
Rough Road Rough Ride
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Al:
I have had vibrations appear on brand new paved highways then on another stretch of newly paved highway I have had no vibration (or far less).
On the other hand I have been on ruff roads and had little to no vibration, then been on ruff roads and had vibration.
There seems to be no rhyme or reason. This is my biggest frustration.
Chuck
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Chuck ,just sitting in recliner and thinking do you have adjustable shocks is it possible they are not adjusted the same say left to right,could it cause vibrations .Not trying to beat a dead horse ,trying to come up with an answer.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
The new paving is not the quality of years past. I notice they now use a vibratory
roller and when you ride on the new road there is a humming noise coming from the tires, and if you look at it after a rain you can see ridges.
The other day I was on a road that looked smooth but I got a severe vibration that came and went for the next 10 miles.
Hasn’t repeated it anytime since.
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Fujimo:
From the records that came with the bus I looks like the shocks were replaced about 6 years ago, they or regular Prevost shocks (non adjustable). Definitely a good thought though.
Gmjdw:
Interesting comment on quality of paving these days. FL ST RD 27 in front of our community was just repaved a couple of months ago and they are already tearing up big sections to redo it again. Guess I shouldn’t be using newly paved roads to judge a vibration.
Chuck
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Vibrations can come from many, many sources.
Leaning on a high school physics class where we watched a movie about harmonic vibrations on big US Navy vessels in WWII or Korea, my experience in the airplane business (especially flying in a Beech 18 with a short red line on the tach in the middle of the engine operating range, pilot said if I left both engines there they shake themselves off the mounts), and the modest of car racing I’ve done …
It can be lots of things … some subtle (difficult to find), some easier to find. Especially when they come and go.
I had a terrible drive line vibration at Road America once … knob on shift lever was a blur. Only third and fourth gear at high RPM. Trans had just been serviced. Called trans guy. Said maybe drive shaft or rear end about to come apart or tires. Went to long time GT-1 driver and his mechanic (similar driveline). Suggested I try another set of tires in the rear. I said these are same tires I used last time out, pressures are right. Wheels weren’t bent when I turned them on jack stands.
Put on a different set of tires, vibration promptly gone. I had the vibrating tires spin balanced next week, they were perfect. I pitched those tires and marked the wheels. Problem never surfaced again.
I’ve learned quite a bit between the airplane biz, racing, and now the Prevost.
1. When I’m confronted with a problem, unless I know exactly what it is (or mostly likely what it is), I start with the easy stuff first. The last thing I do is throw money and time at something.
2. Not every problem is major problem and I don’t have call Jeff Rowe everytime “we” hear something different. In spite of what my wife wants to do.
Good luck figuring it out.
PS: I’m also amazed at the varying road noise and feel on new pavement (or sometimes lack thereof on old pavement) or when you can’t see a difference from one stretch to another.
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Mark3101,
You sold your Bus? I saw it on the Liberty site.
Hope that you find the next bus soon!
Safe travels,
Mark
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Dick:
You make a lot of valid points. Getting Michelin to put on another set of new tires will be a hard sell, don’t have deep enough pockets to fund another new set of tires on my own. Having said that, I had my vibrations down to a minimum (practically un-noticeable) until I had the new tires installed. I will continue to search for other items outside of the tires but continue to lean towards the tires, because the increased vibration showed up as soon as the new tires were installed.
Spoke with JoSam Truck Frame & Alignment in Orlando who has done a lot of work on my coach and was the shop that finally found the out of round old tire, shaved it down and gave me a better ride. JoSam said they have seen (specifically the 365s) larger tires actually rotate on the rim as much as 3″ with in the first 500 or so miles until the tire bead seats to the rim. They suggest driving the coach for at least 500 miles then having the tires rebalanced.
Dick, do you think tire shifting on the rim is a valid issue? Driving race cars that have tires that were just mounted then put out on the track with aggressive acceleration and stopping, have you seen tires shift on the rim? I know it happens on drag racing cars.
Chuck
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Good Morning Chuck – sorry to read your post and can only imagine your frustration.
I actually have been following this post closely, reading and re-reading hoping you have found the cause. By no means am I an expert, yet here are a few thoughts….
One thing that might help, that I don’t believe has been covered, is a detailed description of the vibration you feel.
Is it in the steering wheel, which I understand would indicate front tires, or seat which I understand would indicate rear tires, or do you feel it in both your steering wheel and seat? Can a passenger feel it while seated in the passenger seat?
Also, is the vibration ALWAYS present at a certain speed / RPM?
Perhaps try to duplicate the engine RPMs at a slower ground speed and see what happens. In other words, if when traveling at the “highway” speed when you feel the vibration and the RPM is say, 1450 RPMs, manually engage your transmission and drive at that same RPM, but at say 35mph and see if the vibration exists.
Definitely go back to Jo Sam and have them mechanically check each tire for run out. Yes….a tire can, after mounting and balancing change position on its wheel, creating imbalance.
I cannot find it now, but know for a fact a Technical Service Bulletin (perhaps incorrect name of document) addressing engine vibration that can be felt by placing shims under the motor mounts.
I have also read where bad wheel bearings can cause a vibration.
Perhaps get up to the highway vibration speed when it is occurring, then put the transmission in neutral and coast thereafter to a complete stop. If when placed in Neutral, the vibration disappears, that would indicate a driveline issue.
Perhaps have someone follow you and visually inspect EACH tire when you feel the vibration to see if a particular wheel / tie is hopping / bouncing or can be observed rolling in a non-vertical, wavy orientation.
The person observing could also ensure your bus is not dog-legging down the road.
Does the engine harmonic balancer appear ok?
Might Jo Sam or Prevost have any used & mounted 365s that you could swap out for a test drive?
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Ask them when was the last time they calibrated the balancer.
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Chuck – I am 100% certain – even though I cannot recall the name of it – there is a gauge that is used to check a tire for run out / out of round and it is absolutely positively used when the tire is still mounted on the vehicle.
I would definitely try to find a place to check for “run out” in this manner – while the tires are still mounted on the bus. They raise the bus and spin each tire by hand to determine how many thousandths of an inch they are out of round.
It would be ideal if Jo Sams could do this since they also have a tire trueing / shaving machine.
Maybe just make an appointment at Jo Sams for this with time allotted to have ALL the tires trued. Or just go get them all trued at Jo Sams.
***Another thought since you said a vibration has always existed… Could it be a warped disk brake rotor? Centramatics advertise they balance the tire and the hub, yet centramatics can only balance up to (if I recall correctly) 16 ounces off.
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Al:
Just tried putting the bus in gear F & R with brake on and increasing the throttle a little. Engine did not move in F or R so I would guess trans and motor mounts are OK.
Jeff:
I feel the vibration mostly between 58-64 MPH. Sometimes at a little more or less speed, but most of the time at speeds indicated above. Going above or below the noted speeds will usually decrease the vibration and although the vibration is present most of the time between 58-64 MPH occasionally it is smoother in that speed range (although not often).
Duplicating the RPMs at a lower speed by shifting into a higher gear is a good I idea. I will try that the next time I have the coach out.
JoSam found the original out of round passengers tag by doing what you described (Lifting each wheel while on the coach, spinning and checking for trueness of each tire). JoSam also used a tire iron and tried to move each tire up & down while the wheel was off the ground and on the coach to check the wheel bearings. All bearings appeared to be OK.
Not sure if I am comfortable putting the transmission in neutral while going down the highway. There are numerous warnings to not tow a bus while drive shaft of rear axle is in place allowing the wheels to turn while trans is in neutral.
I do plan on having a neighbor drive along side of me once I get back home. Working out of town right now and living in the bus.
My biggest issue right now; I purchase the tires through Michelin and they designated Boulevard Tire (a national franchise) to mount and install the tires here in Ft. Lauderdale, FL. The Ft. Laud store does mostly tractor trailers and they (without actually saying it) pretty much let you know as a motor home you are in their way. Its been a battle just getting them to balance the tires. They wanted to just mount and install. I stood right by the installers side as they mounted and balanced them. Not to sure the would rebalanced without an argument or half A.. attempt. I may have to go back to JoSam and pay out of pocket to resolve this issue.
Great customer support. NOT!
Chuck
P.S. Michelin made Boulevard tire replace the drivers tag right after installation because the original one took 18oz to balance. Boulevard has charged my card full price for the second tire they put on the drivers tag without my authorization. Fighting to get that $ refunded.
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Install a set of Koni’s when you have a shop appointment. I read your shocks are regular grade which raises a red flag.
You never commended if they shocks were dry or showed signs of leakage. At 6 years it’s time for a change to Koni.
On my 3 buses Centramatics and Koni shocks all the way around.
We’re good to go.
AL
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