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Old 03-31-2009, 01:36 PM   #1
GOPAPA
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Truck Vibrates And Shimmy's At 50 MPH

My sons truck

This is a before and after picture of his truck.. He drove it after we put the all colored front clip on for 6 months or so and no problems .
Now it has problems with vibrating at 50 MPH ,,pretty bad.

The wheels on it now are what he drove on it before the wreck and after .

He had the front tires balanced ..he says the wheel berrings are pretty tight ,,hardly no movement by shoving in on top of wheel and pulling out on bottom ,,while jacked up..

It has sit out side through all weathers for close to a year ..

So,, why all of a sudden after driving with no problems ,,it now has this terrible vibrating a only 50 MPH ? papa



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Old 03-31-2009, 01:56 PM   #2
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Re: Truck Vibrates And Shimmy's At 50 MPH

Carrier bearing going out?
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Old 03-31-2009, 02:06 PM   #3
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Re: Truck Vibrates And Shimmy's At 50 MPH

^ x 2 ^, PL
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Old 03-31-2009, 02:14 PM   #4
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Re: Truck Vibrates And Shimmy's At 50 MPH

Check the drive shaft as stated. I would check the wheel bearings and repack them also.
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Old 03-31-2009, 02:41 PM   #5
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Re: Truck Vibrates And Shimmy's At 50 MPH

My wife's corolla develops this problem a couple times a year when the tire pressure gets to low, the wheel vibrates really bad, air 'em up and the vibration is gone. If it's been sitting for a long time, check the tire pressure. Could be that simple.
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Old 03-31-2009, 03:07 PM   #6
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Re: Truck Vibrates And Shimmy's At 50 MPH

My son first thought a wheel droped a wieght but when he had them balanced they were good and at that time they were checked for air loss..
He also said he got under it and shook all parts including the drive line and found no wobbles.
I suppose that the carrier bearing might not tell you this ,,and only under high speed show up..
How do you go about proving that the carrier bearing is good or bad ?
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Old 03-31-2009, 03:22 PM   #7
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Re: Truck Vibrates And Shimmy's At 50 MPH

Larry,
You might check the U-joints too.
I'm not sure how to explain it, but I'll give it a good soldierly try.
It could be that they're "tight" and not "bending" like they're supposed to. So you may want to give them a good shot of grease & maybe that'll free 'em up, if that's the problem.
But, if they've reached that stage, they're probably junk anyhow.

Do you happen to know a drive shaft guy that could check the balance on the drive shaft?

Just some ruminations on my part.

LJ
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Old 03-31-2009, 03:37 PM   #8
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Re: Truck Vibrates And Shimmy's At 50 MPH

Quote:
Originally Posted by El Jay View Post
Larry,
You might check the U-joints too.
I'm not sure how to explain it, but I'll give it a good soldierly try.
It could be that they're "tight" and not "bending" like they're supposed to. So you may want to give them a good shot of grease & maybe that'll free 'em up, if that's the problem.
But, if they've reached that stage, they're probably junk anyhow.

Do you happen to know a drive shaft guy that could check the balance on the drive shaft?

Just some ruminations on my part.

LJ
thanks El Jay ,, any of those sugggestions sound plosible and I will call him and bring them up to him.. the grease in the U-Joints might be what is missing as ,, it has been sitting through a summer and fall and winter out side,,
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Old 03-31-2009, 03:52 PM   #9
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Re: Truck Vibrates And Shimmy's At 50 MPH

How recent was the tire balance? Before or after the shimmy and vibration. Mine did the same thing and I couldn't figure out for the life of me why. Then one day I was trying to run an errand in the truck (even with the shimmy) and BLAM! my front tire exploded. Then it all came back to me. A friends Suburban did the same thing with a rear wheel on a trip we made to Buttonwillow CA. a few years back. Bad tires on both.
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Old 03-31-2009, 04:17 PM   #10
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Re: Truck Vibrates And Shimmy's At 50 MPH

rechecking wheel balance and that lugnuts are tight on all four would b first on my list followed by inspection of monting hardware of the control arms, then checking the motor mounts ,driveshft ujoints and carrier bearing, i'd also check that the front crossmember is securly fastened to the frame, ball joints tierod ends etc
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Old 03-31-2009, 06:55 PM   #11
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Re: Truck Vibrates And Shimmy's At 50 MPH

I would also check the rear , loose u-bolts and worn perches (egg shape bolt holes ) traling arms and it's parts and all thats been mention already
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Old 03-31-2009, 07:11 PM   #12
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Re: Truck Vibrates And Shimmy's At 50 MPH

drive the truck at the speed it shakes. Ask yourself, " where do I feel the vibration? Is it in the steering wheel? Or do I feel it in the seat of my pants. After what you have tried, I would think it is a drivetrain problem. If you replaced the whole front clip, I wonder if something is in a bind? Maybe like someone else posted is the carrier bearing shoved back?
I would think this is a trial and error thing, and when you find it, you will go " why did I not think of that first ". I would loosen up the motor mounts, and the trans mount, wiggle the motor and trans, and pay close attention to what happens when you loosen the bolts. Did the motor/trans move? Get everything where you know it should be, and then drive the truck.
YA KNOW IT KIND OF LOOKS LIKE LONGHORN MANS BURB WITH THE NEW CLIP ON IT!!!
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Old 03-31-2009, 07:18 PM   #13
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Re: Truck Vibrates And Shimmy's At 50 MPH

All good suggestions.
As he changed the front clip and it vibrates afterwards what else did he change?
Reason for changing front clip? If it got in a wreck there may be a bent piece in the suspension or steering.

As the others have said I'd check the balance on the wheels again but I would also check=
For and out of round tire or one with a broken belt.
For a gob of dirt/mud inside of one of the rims.

If he changed a drum lately, I have seen at least one drum that was so far out of balance new out of the box that it couldn't be run.

I'd try to find someone with an on the car/truck spin balancer that could spin the wheels on the truck to try and find the vibration that way.
If it doesn't have posi you can jack one rear wheel up at a time and run it up in gear to see if either of the rear wheels are the problem. You should be able to check the driveshaft at the same time too.

When I was doing front end and brake work on a daily basis I ran into more than one guy who didn't think that the rear tires could cause his vibration as they were on the rear.

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Old 03-31-2009, 07:24 PM   #14
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Re: Truck Vibrates And Shimmy's At 50 MPH

Check you crossmember bolts that are bolted to the frame...I had the same problem until I retighten them.
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Old 03-31-2009, 07:37 PM   #15
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Re: Truck Vibrates And Shimmy's At 50 MPH

Mr48chevy, I used to have a spin balancer back in the day, MAN what a great piece of equipment!! Balanced everything that rotated at every corner. I still have a scar on my arm from getting too close to the tire that was spinning 60+. Wonder if you could still buy one of those -----
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Old 03-31-2009, 08:38 PM   #16
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Re: Truck Vibrates And Shimmy's At 50 MPH

It have your answer. It isn't a cheap fix, but I would bet it is your tires. I had the exact same issue with my 91 chev. I had cheap old tires, and I let it sit for a couple months and then it developed a shimmy. The belts went bad in the tires. If you can borrow some tires from somebody for a test drive, then you can rule out bad tires.
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Old 03-31-2009, 08:53 PM   #17
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Re: Truck Vibrates And Shimmy's At 50 MPH

If the tires have flat spots, they should go away when they get warmed up. If not, then spinning them on a balancer should allow you to look at them and see the flat spot. If you can "help" then you can hold something in a fixed position and see if there is a fluctuation as it rotates. It doesn't have to be powered, just turning slowly and checking for an out-of-round state.

As for the driveline, u-joints that have rusty bearings could be the issue. As stated earlier, a tight u-joint will cause a vibration. It doesn't take much rust to tighten up the clearances within the cross and roller.
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Old 04-01-2009, 06:27 AM   #18
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Re: Truck Vibrates And Shimmy's At 50 MPH

Quote:
Originally Posted by BluTrukker View Post
It have your answer. It isn't a cheap fix, but I would bet it is your tires. I had the exact same issue with my 91 chev. I had cheap old tires, and I let it sit for a couple months and then it developed a shimmy. The belts went bad in the tires. If you can borrow some tires from somebody for a test drive, then you can rule out bad tires.
Good advice. This type of vibration at a certain speed is almost always a tire problem. Balancing often will not help.
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Old 04-01-2009, 10:48 AM   #19
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Re: Truck Vibrates And Shimmy's At 50 MPH

You say it was good for awhile after the accident and the tires were checked for balance.And,the balance was good?Maybe something worked loose since it`s droiven after the accident.The shimmy is felt in the steering wheel,as in more than just a transfered vibration.More like the wheel wants to rock back and forth.Did you check side to side play as well?It could be the tie rod ends.Ball joints will make it bounce and that`s how a bad or loose bearing feels,like the tire`s bouncing.
I`d try on some other tires.Can you borrow some?Try rotating and see if the vibration moves or stops.
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Old 04-01-2009, 07:23 PM   #20
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Re: Truck Vibrates And Shimmy's At 50 MPH

I will see him tonite and let him know all the suggestions from you all.. thanks papa
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Old 04-01-2009, 09:43 PM   #21
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Re: Truck Vibrates And Shimmy's At 50 MPH

How about running it at 50 mph in a lower gear? Would that separate a tire problem from everything else ie: speed vs. rpms?
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Old 04-01-2009, 11:16 PM   #22
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Re: Truck Vibrates And Shimmy's At 50 MPH

around our shop most vibrations that can be driven thru are tire related
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Old 04-02-2009, 07:53 AM   #23
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Re: Truck Vibrates And Shimmy's At 50 MPH

Check your shock absorbers.
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Old 04-02-2009, 08:07 AM   #24
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Re: Truck Vibrates And Shimmy's At 50 MPH

Definately look at the tires.Even if you don`t have another set laying around,rotating with move the problem and produce a different result.A bad tire up ront will exaggerate front end wear and will be felt in the steering wheel more than if it`s on the rear.On the rear you`ll notice the rear bed corner vibrating or hopping more than the other side.
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