1996 Yukon 4 X 4 Troublesome Vibration

All:
I have had a persistent vibration commencing at 66 MPH and continuing from
there thru 80MPH. I don't (won't) run faster than that. The Yukon has
120000 miles and had the transmission replaced with a GM Certified rebuilt
at about 98000 and then replaced with another Certified transmission after
only 8000 miles under the warranty. I just put a new set of Michelins on it
and complained to my tire guy about the vibration. He clocked the tires and
then after the vibration was still there he replaced two of the four new
Michelins. Vibration is still there and we are all puzzled. The universal
joints seem tight with no play and none of the usual symptoms of a bad U
Joint. I'm now suspecting that in the process of replacing the
transmission(s) that the drive shaft got bent or is out of phase or somehow
got a balance weight knocked off. I do get a slight double clunk when
shifting from reverse to drive and back to reverse, but no noticable clunk
when going from park to drive.
The truck is as smooth as silk until it reaches the "magic" 66 MPH.
Any suggestions or hints on where to look would be greatly appreciated. I
no longer feel I can trust GM dealers. We live in North Carolina.
Thanking you all for your insight in advance.
Bob
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On Sat, 6 Oct 2007 21:06:03 -0400, "Robert Clark"

First check to make sure your front and rear u-joints are aligned properly (unless you have a slip-yoke) and that there are no rocks stuck in the vanes of your disks. Then put the truck up on cinder blocks, give it a run and see what's shakin'. I doubt that either of your axle shafts are bent. I would bet that either your driveshaft is out of balance, your tranny output shaft bearings and/or differential pinion bearings are shot, or both. Whatever it is, you'll see it when it's off the ground and running.
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On Sun, 07 Oct 2007 02:17:50 -0700, Frank Gilliland

Personally I would have rebalanced driveshaft long ago because this sounds like a drive shaft balance problem. Shaft are not balanced that good to begin with at factory and with time/age, stress and rusts they can go futher out of balance. Take the rear drive shaft off and take it to a drive shaft shop not the dealer (they will have to send it out and charge you more for it) and have it checked and rebalanced. DO this and your problem will likely be solved. This is often overlooked. ----------------- TheSnoMan.com
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wrote:

If this Yukon is a 2dr, then the shaft is short and susceptible to vibration if not balance right or if the U joints are a tad worn.
Cheers
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An area you might want to check:
Take the wheels off while on jack stands, and put all the lug nuts back on.
Start it up, then put it in gear, look to see if the rotors and drums are running out. (As in them being out of round)
Also, the 4l60E transmissions, as well as some 4L65E transmissions have a known problem, with the planetary gears stripping. Causing a vibration, which is hard to trace.
RK

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I believe I read that the OP had the truck to a shop to replace the U-joints or Pinion seal. The drive shaft had to be removed. I'm betting that the drive shaft was put back in 180 degrees off from the original position. That will almost guarantee a high speed vibration. Regards, JR

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On Mon, 08 Oct 2007 01:11:14 GMT, "Refinish King"

YOu would be able to tell this under varing power levels and range selections. I do beleive this is purely a drive shaft issue. ----------------- TheSnoMan.com
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To the Group:
My vibration problem was partially a drive shaft issue, the rear universal was to quote the machine shop "wallowing about". The drive shaft was balanced and a new U joint installed. Still have the vibration. Not as much but it is still there. There's nothing left that rotates except the rear axle and the brake drums. I'm at a loss as is the guy who removed the drive shaft and reinstalled it. It seems to reach a resonant frequency at 67 MPH and it stays through 80. The vibration is less than it was before the new universal and balancing but it's still there. The only thing I can think is an inner axle shaft bearing. It is definitely coming from the rear. Motor and transmission mounts are all good and show no signs of deterioration. There is no evidence of looseness when the rear wheels are jiggled. He ran the vehicle on the lift at 80 and saw no evidence of out of balance or wobbling in the rear wheels. I'm stumped.
Robert
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On Thu, 11 Oct 2007 21:32:03 -0400, "Robert Clark"

You might pull rear axle shafts and maket sure they are true/straight and bearings are okay. Pinion yoke could not be true or maybe be out of balance too. ----------------- TheSnoMan.com
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I'd have it rebalanced. My last foray in having someone rebalance my shaft resulted in 2 trips to get it right. I have the short shaft on the 2dr. And its been 110000 miles so far.
Cheers
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Change the rear tires for the front ones. might be a balance problem. old john
Hello, Martin! You wrote on Fri, 12 Oct 2007 23:25:24 GMT:
MR> Cheers
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piece of shit chevy
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