Vibrations

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Black Fox
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Vibrations

Post by Black Fox » Sat Jan 13, 2007 12:16 am

Gents

My HMMWV has recently developed a vibration. When the engine is ideling I can feel it in the seat, pedals & steering wheel. When I accelerate the vibration increases but as I get to higher speeds it starts to fade. When I get to 50+ it's not really noticiable. My suspision is that it might be a motor mount but I'm not a mechanic. Any help you can provide would be appreciated.

Thank you

Darrell
1986 USMC M-1044 HMMWV
1984 M-101 A2


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Post by artificer » Sat Jan 13, 2007 1:17 am

Generally a fairly smooth idling engine should not exhibit engine mount vibration...would more likely be noticeable on hard acceleration or deceleration. It may pay to explain better what you mean by your vibration.
With this type of specialty vehicle it would probably be a "known thing" to other owners and I'm not one, if they understood better.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

Black Fox
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Post by Black Fox » Sat Jan 13, 2007 1:40 am

There is a vibration at all times except at higher speed. Idle and slower speeds its stronger. Higher speeds it weaker. The vibration is the strongest when accelerating from a stopped position. When you let off on the gas there is still a vibration but weaker. It vibrates even when the gears are in neutral.

This is something that has been growing over a period of time. Initially I thought that was just the nature of the vehicle. I've never driven another HMMWV so I have nothing to compare it with. But it's obvious now that it's something more.

By the way, oil and transmission fluid seems fine. Also, the engine sounds fine.

The only other mechanical issue that I'm aware of is that my steering gear box has a small leak. Other
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1984 M-101 A2

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Kurt Lesser
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pickin' up bad vibrations

Post by Kurt Lesser » Sat Jan 13, 2007 4:59 am

Black Fox,

Vibrations that go away at speed can be caused by any number of things in the HMMWV. Sometimes things seem to settle down when they're moving faster. Good examples are harmonic balancers on the crankshaft and bend pulleys on pumps. There are umpteen laces on the driveline that can also cause vibrations. Sounds like a little exploratory surgury might be necessary.

I'd get the creeper out and plan to spend some time rolling around under the beast. You didn't mention and clucking noises associated with the vibration but I'd take a good look to make sure that all the bolts that attach the half shafts to the disc brake rotors are tight, and all the U joints feel good. You might want to pull the wheels and check the bolts that hold the half shafts to the geared hubs too.
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Re: Vibrations

Post by sergio » Sat Jan 13, 2007 5:20 am

Not the typical symptoms of a flex plate but I'd still check it for cracks and/or loose bolts.

JP

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Post by cpl brown » Sat Jan 13, 2007 8:23 am

how is your fan? or fan hub ,,,to me i would start looking up front of the engine, with out seeing it,,,, the harmonic balancer is a great place to look

i would look into the motor mounts also ,,most of the time its the drivers side

the one thing that you said is that it does it sitting still, so start looking around while its running

a loose flex plate can be a problem and even if your transmision bell housing bolts start to back off this could hapen also

one tool that will help can be stethascope sounds kinda wierd but this tool can help in alot of ways ,,,auto parts stores have them

good luck
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ron alred
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vibration

Post by ron alred » Sat Jan 13, 2007 4:06 pm

THE TORQUE CONVERTOR HAS WEIGHTS WELDED ON IT. IT IS POSSIBLE
THAT ONE HAS CAME OFF. ALSO CHECK
THE HARMONIC BALANCER TO SEE IF THE CENTER METAL HAS TURNED IN THE RUBBER PORTION OF THE BALANCER. THIS SHOULD BE THE ONLY TWO THINGS TO BECOME UNBALANCED. ALSO BE SURE THE BELTS DO NOT HAVE A SECTION MISSING FROM ONE. THANKS RON


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