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Vibration-Am I missing something?
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There is a Prevost Service Bulletin, Instruction Sheet titled,
“REDUCTION OF HIGH SPEED VIBRATIONS ON VEHICLES EQUIPPED WITH DETROIT DIESEL SERIES 60 ENGINE”,
that appears to be applicable to your coach. Seems to suggest that maybe driveline angles might be causing the vibrations in some cases. Maybe take a look at it and see if it is something to consider or not.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
I really dislike giving my thoughts, about anything, but as long as no one comes back and gives me a bunch crap I’ll give ya couple of things to toss around, my experience, some time when ya had a seal replaced the axle may have been knocked over, happened on couple of my trucks. Then the drive shaft may be out of balance, there are balance rings you can put on to take care of that. Good luck
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Al:
Will put Koni’s on and probably put Centramatics back on again. Do you know the Koni’s part #s I will need?
Tim:
Thanks for the link. Will look into it. Great info, Thank you.
Dick:
Funny you would mention drive shaft seals. About a year ago Prevost Winter Garden put one in on the drivers side, couple months later passengers side started leaking, couple of months after that the drivers side starting leaking again and had to be redone. Knowing Prevost did the work I would hope they would have been careful, though you never know. How big of a deal is it to install the balancing rings?
Chuck
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Chuck
Reason for not towing with trans in (N) is due to lack of lubrication inside transmission. Most if not all internal trans parts are lubricated by the transmission’s own internal pump (which supplies line pressure for shifts, clutches apply/release etc. This pump is driven (normally) by the input shaft via the torque converter – which is driven by engine’s crankshaft.
So in a towed situation (without the bus engine running), if you don’t pull axles or driveshaft, the output shaft on transmission continues to turn as the wheels roll – spinning internal transmission parts without adequate lubrication since bus engine and trans pump are not turning.
Hope that made sense. I can’t see any issue shifting to (N) while moving and off throttle, I would THINK the electronics would allow for smooth gear re-engagement when requested but haven’t tried that so not 100% sure. It has been no issue on any trans I’ve had with manual shift linkage, wouldn’t think electronic keypad would be a problem but again haven’t tried it.
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Where do you feel the vibration? Steering wheel only? Driver Seat only? Passenger Seat? All three locations? Is it constant or intermittent?
For the money, I would (re) start by trueing all tires.
I also would manually check your centramatics to ensure the inside media moves / flows inside the tube. I replaced my steer and tag centramatics following this inspection as the media was frozen in place.
Call Centramatics to confirm how much weight they can off-set and try not to add lead weights unless they are the tape-on style, but best to not add any.
Not familiar enough as to where in FL you are currently located, but St. Lucie Tire & Battery also trues tires at their commercial truck location in St. Lucie. St. Lucie B&T is talented and can also re-inspect your suspension components. They install new tires and suspension components for Liberty Coach. They also true all newly installed tires for Liberty.
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Jeff:
Vibration is noticeable in floor, but most noticeable in the center of the bus in the dinette table and the shelf’s in the refrigerator shaking. A glass of water on any surface while driving shows vibration in the water, again more so in the center of the bus.
I did have Centramatics but had them removed (Centramatics refunded me the cost) after their inability to correct the vibration on the older tires. Looking back the old out of round passenger tag was the issue and once shaved the coach ran much better. Blaming the inability to balance on the Centramatics was incorrect.
Jon’s comment in this post on 12/30/2020 “Long ago I used wheel weights, but found them to be temporary” is defiantly a valid statement and a good argument to going back to Centramatics.
Chuck
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Chuck: yes the tires can move on the wheels, especially at the pressures used on race cars (15 to 25#). The pro teams use a paint pen to mark up the tires (date, track, set number, spring rate from sticker, number of laps, and a “V” pointing at the valve stem) and they move. Especially at tracks where long, heavy breaking is used (Martinsville, road courses).
Might be a good idea to mark the valve stem location on our tires. At 85 to 120psi I’d be surprised they would move, but the diameter of the tires on the bus vs 15” racing wheel give the bus more or less leverage to move the tire on the rim?
Couldn’t one use a machinist’s dial indicator to check for run out. Or must a special device be used?
I think the three axle alignment could be checked with a string and jack stands like we do with the race cars. I’ve never tried it on 45’ coach. You’d almost have to do it inside so no wind. But if a good three axle alignment shop wasn’t close by, it might be worth a try.
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Dick:
JoSam’s did use a dail indicator on the old set of tire, that’s how we found the out of round passengers tag. Guess I will have to do it again with the new set of 365s.
JoSam also did a 3 axle alignment about 10 – 12 months ago and also adjusted the ride height before aligning.
Chuck
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drive shaft. Has it been removed or rehabed before problem started?
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I figured a good machinists dial indicator should be able to get the job done.
Robert makes a good point.
I’ve had the driveshafts on the race cars straightened and balanced a few times (turning 8500rpm with a 4.76 rear end it made a difference). Any good driveshaft/driveline shop can check it for straightness and balance it. I’d be stunned if it was bent (but you never know) and balancing is pretty quick. At the RPMs the drive shaft turns (pretty low) its an unlikely source, but still possible. Easier to pull the driveshaft and have the work done than to futz with the tires.
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Here is a Michelin 365 tire mounted correctly on rim. Check your tires showing this 1/4 inch appox completely around the rim.
Jon, has gone into great detail on this subject, along with tires rotating from the installed point.
Before going to a tire shop for shaving these $1000 tires this is an easy inspection.
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Chuck ,you mentioned Jo sams used a dial indicator to find your old tire out of round.Can you check to make sure rim is not bent or having any in and out run out.
2000 Featherlite H3-45
2024 Jeep Grand Cherokee
Leesburg, FL -
Robert:
Have not had drive shaft rehabbed. It was out last year when Prevost Winter Garden changed the universal joint.
Dick:
JoSam did spin up the rims on the tire machine and check with a dial indicator a little over a year ago when they had the tires broken down to remove the beads that were inside. Rims were OK.
Al:
Have read Jon’s post and stood there while tires were being mounted to make sure they were mounted horizontally and the indicator line on the tire next to the rim was even all the way around.
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did vibration start after prevost changed universal? There is a clocking problem I have had in past when reinstalling.. drive shaft not orientated in sequence.
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“There is a clocking problem I have had in past when reinstalling.. drive shaft not orientated in sequence.”
This could be big!
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