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Discussion Starter · #1 ·
I am trying to pin down a vibration that I get at 50-80 MPH on my 2007 Ram QC Thunder Road 5.7, which has 50K miles and which I recently purchased. I feel the vibration primarily in the seat and the empty passenger seat visibly vibrates. There is very little vibration coming through the steering wheel, so I assume my problem is related to the rear wheels or axles.

As soon as I purchased this truck I had new Cooper Discoverer tires mounted on the OEM 20"x9" Chrome Clad wheels and they have been balanced on a Hunter Road Force balancer. The Hunter balancer reported that both rear wheels/tires were borderline failures, but they did balance. To ascertain if a defective tire was the cause, my tire guy replaced one of the new rear tires, but that did not change anything.

I jacked the truck up and had my wife put it into gear and neither rim appears to be warped or bent, at least not to the eye.

The shocks could be worn, but the truck does not bounce like a vehicle usually does when the shocks are worn out.

While I had the truck jacked up, I placed a long bar under each rear wheel and applied upward motion (like you do when you are checking front ball joints). Both rear wheels will move vertically a little bit, I am guessing about 1/16 of an inch. There is only a very small amount of horizontal play, which, I am told, is normal.

My questions: How much vertical play should there be in the rear axle bearings? Could this cause vibration similar to an unbalanced wheel?

What other issues could cause this vibration? Thanks for your help!!
 

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A very small ammount of play is somewhat normal. Jack it up on all fours and get someone to take it up to the speed that the vibration occurs in. If its a wheel bearing you should be able to hear it this way.
 

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Discussion Starter · #3 ·
Actually, I did have both rear wheels up and spinning (I have limited slip so I had to) and I did not hear any unusual noise from the bearings up to 30mph. I will try it up to a higher speed.

I just did not expect any vertical (up and down) play at all in the bearings so I felt I should ask....

Thanks!
 

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Discussion Starter · #4 ·
Bucks, I do not hear any unusual noise from the bearings when I jacked the truck up and ran it up to speed. I think I have located and fixed my vibration by having my tire guy replace both of the new rear tires, but I still need to know about these bearings...

I had a Ford that made no noticeable noise from the bearings until it was too late....they had shed enough metal into the differential to trash it....a costly mistake on my part.

When I noticed this small amount of play in these Ram bearings I felt that it would be prudent to find out how much play, if any, is normal before the same thing happens to this Ram as it did to the Ford. I have never noticed any play in rear axle bearings on any other vehicle before unless they were shot.... I now that some "in and out" horizontal play is normal but I did not expect to find the "up and down" play....

Anyone know how much play, if any, is ok?
 
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