Vibration between 70 and 80 MPH

[woyster_00z71]

First some history... For the past year or so now I have been trying to get rid of a squeak/squeal that my wife has been hearing on my 2007 Avalanche. I have gone down many different avenues including rear brakes, front hubs, u-joints, all 4 shocks, and finally front brakes. The squeak/squeal was finally fixed...not sure why it was the front brakes as they were the newest of anything when the search for the squeak/squeak began.

 

In any case, prior to changing the u-joints there was no vibration. Afterwards, there is a vibration that begins at about 72 MPH and gets better at around 78 MPH (roughly 70 to 80). I changed out the u-joints myself and I have checked and rechecked my work. The stock waxed-in u-joints were removed and replaced with MOOG/Precision part number 234. After reading some posts on this and other forums, I even rotated the yolk and driveshaft 180° as recommended by some.

 

Being at my wits end, I took it to a local shop last week to have them look at it and see what they thought the problem was expecting them to have to balance the driveshaft. The shop checked everything and gave me kudos for the workmanship stating that it is "better than they have seen from some other local shops". They said everything looked fine with the driveshaft...no missing weights, no apparent damage from the u-joint swap. They concluded that the speed-specific vibration was a tire issue and recommended that I have the tires balanced/rotated. After balance and rotation, the vibration still remains. The tire shop did a thorough inspection of the wheels and tires while performing the balance/rotation and said everything looked good (by the way, these are the same wheels/tire before and after the u-joint swap).

 

Where do I go from here? Do I take it back to the shop and pay the "several hundred dollars" to have the driveshaft removed and balance checked? The shop is reluctant to do this as they said a driveshaft vibration will begin at lower speeds and just continue to get worse as speed increases. I give them credit for not trying to get me to do unnecessary work. Did I use the wrong u-joints? Is there a make/model or part number that I should have used instead? Is there anything else that I should look at?

 

Just a thought...could it have anything to do with the shocks? Those were replaced the same time as the u-joints. I don't see how it could be related, but just thought I would throw it out there as I'm at a loss here.

 

Thanks in advance for your help!