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Author Topic: Odd Vibration MC8 45-55mph  (Read 2725 times)
Melbo
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« on: August 21, 2011, 08:04:15 PM »

I get an odd vibration when accelerating from about 40 to 50 or so.  I was thinking it might be front wheel bearings but it doesn't show up consistently so I am a little lost.

I haven't noticed it at all when coasting or maintaining a constant speed just when I'm accelerating and then only in the speed range mentioned.

I would rather fix something when I'm home than when I'm on the road -- called good judgement I think.

Any opinions (I know I'm taking a chance with that) YES ANY opinions appreciated.

Thanks

Melbo

P.S. I am hitting the road again soon  Grin
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eddiepotts
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« Reply #1 on: August 21, 2011, 08:24:04 PM »

I am sure it could be 100 differant things but the only vibration I ever had like that was my drive shaft bolts were coming loose. give us more info. do you fell it in tour steering wheel, seat or in the structure of the whole bus.
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Ed Hackenbruch
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« Reply #2 on: August 21, 2011, 08:39:05 PM »

My first thought was also u joints. Smiley
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Melbo
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« Reply #3 on: August 21, 2011, 08:44:09 PM »

The driveline is fine --- Was just lubed and checked before the last road trip and nothing was amiss --- it really isn't something that a passenger would notice -- I can feel it in the steering wheel -- the front wheels were balanced when I put the new tires on somewhere less than 7 thousand miles ago.

The drives all have balancing powder

I hope this helps --- I also freshly lubed all the suspension about 2500 miles ago

Melbo
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Ed Brenner
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« Reply #4 on: August 21, 2011, 08:54:24 PM »

Check to see if you thru off a front balance weight, steering wheel vibration especially at that speed usually indicates a front wheel or
loose front end part.(at least in the automotive world). Same difference just bigger stuff !!
THanks ED
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luvrbus
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« Reply #5 on: August 21, 2011, 09:24:37 PM »

 happens only when accelerating at certain speed diffidently something in the power train,Jim had that problem and his was caused by the ring gear bolts coming loose on the cage hope that is not your problem

good luck
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Melbo
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« Reply #6 on: August 21, 2011, 09:31:54 PM »

The bus was parked for over six months before this last trip --- is it possible that the tire or tires developed a flat spot??

Something loose in the diff does not sound good --- how would that be checked??

Melbo
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Lin
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« Reply #7 on: August 21, 2011, 10:22:30 PM »

Does it do it also after you have been driving a while?  Tires can get out of round just sitting for long periods, but recover when they get hot again.  Anyway, after giving everything a good shake, re-balancing may be worth a try.
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Rick 74 MC-8
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« Reply #8 on: August 22, 2011, 05:29:14 AM »

can you feel the speed of the vibration? example wheel speed, drive shaft speed, engine speed. can you change gears?  Does that change the speed of vibration



      Rick 74 Mc-8
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luvrbus
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« Reply #9 on: August 22, 2011, 06:26:15 AM »

Mel, if you think it might be the tires up the pressure to close to max and see if that changes the range of the vibration but doing only on acceleration sounds to me like something does not like that torque range could be a rear wheel bearing going bad,and about the only way you can really check the U joints on 1 is pull the shaft and remove the caps they will be tight as a drum and be wore out   

good luck
« Last Edit: August 22, 2011, 06:35:09 AM by luvrbus » Logged

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lostagain
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« Reply #10 on: August 22, 2011, 06:38:25 AM »

After driving for a while, feel the wheel bearings with your hand. A bad bearing will be hotter than the others.

JC
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Lee Bradley
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« Reply #11 on: August 22, 2011, 10:23:14 AM »

How did you check the u-joints? The only way I trust is to disconnect the u-joint and work it through it's full range of movement. I'm guessing you have a seized u-joint that you can feel when the acceleration torque changes the drive train alignment; below 40 mph its not turning fast enough for you to feel and above 50 mph you don't have the torque to cause enough misalignment.
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Chopper Scott
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« Reply #12 on: August 22, 2011, 10:54:26 AM »

Two things come to mind also. Definately check those u joints disconnected but also check your rear housing pinion bushing and also the tranny bushing for looseness. I had a similar problem in a pickup and it turned out to be the tranny bushing. later
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« Reply #13 on: August 22, 2011, 01:53:42 PM »

The bus was parked for over six months before this last trip --- is it possible that the tire or tires developed a flat spot??

Something loose in the diff does not sound good --- how would that be checked??

Melbo

I am replacing to tires right now as a result of flatspots.  I only felt the vibration at medium range speeds.  When I got up to 60 I couldn't feel it.  45 to 50 I could feel it.  Especially on the first black top road leaving home.  It was as if the tired heated up and it calmed it down a little.
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Melbo
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« Reply #14 on: August 22, 2011, 07:50:02 PM »

Ok I looked up the invoice for the drive line and the slip yoke was built and balanced 8/28/2008

It has been lubed five times since it was installed --- I'm wondering if the heat gun would tell me if there is a problem.

I will be adjusting brakes and lubing it up before I hit the road so here is my plan.

I am going to air up the tires (per Clifford) --- Adjust the brakes and lube it up.  Check the oil level in the front hubs and tags.  The bolts that hold the driveline in place are one use bolts so I don't really want to drop it but if the consensus is that it must be done I will do it.

Then when I am on the road I will check the temps of the hubs on the steers and  tags the drive hubs and the temps of the universal joints in the drive line when I get about 50 or 60 miles down the road.

This has bugged me for a long time --- I have jacked the bus up and run each side off the ground to see if it was wheel bearings. I have replaced the tires with michelins. I have had the diff gear set replaced. I have replaced the driveline TWICE the second time is referenced above. The bus is MUCH better than when I started. It is quiet and pleasant to drive but I don't want problems on the road so this odd vibration means something and I would like to find and fix it.

Melbo
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If it won't go FORCE it ---- if it breaks it needed to be replaced anyway
Albuquerque, NM   MC8 L10 Cummins ZF
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