Vibrations

[goldata81]

I had a vibration at 45-55mph on my ’07 Yukon that appeared shortly after having the 6L80 replaced at 191k. I first thought it was most likely the tires so I had them rebalanced and rotated which seemed at first to do the trick but was not the case. I suspected the new reman’ed trans next since the original ujoints were replaced at 135k with Moog units and they seemed nice and tight upon inspection.

I downloaded an app on my phone called Accelerometer Meter to help narrow down where to look. The app has a Spectrum analyzer that will save a snapshot of the amplitude of x,y and z axis of your phone’s accelerometer across several frequencies. My phone fit tightly in the center console lid cavity\depression(you'll want your phone firmly attached to your vehicle to sense the vibrations). I just ran the analyzer and got to where I could feel the vibration the worst with my phone lodged in that console cavity and hit the save button. The saved data will give you several frequencies and the their amplitudes in x,y and z. Look for higher values/spikes in any of those axis for the given freqs listed out. When saving the data, make note of your speed and trans gear and maybe engine speed. With that info you should be able to ballpark the speeds your wheels and from that use your rear end ratio to get your driveshaft speed. If you can find spikes in the saved data, you’ll just need to figure out what is spinning at that rate in rotations/sec to narrow down where to look.

On mine, it was a ujoint that the needle bearings were ground away. I found it this way but would have never suspected it from my inspection.

 

[Erickk120]

I had a vibration at 45-55mph on my ’07 Yukon that appeared shortly after having the 6L80 replaced at 191k. I first thought it was most likely the tires so I had them rebalanced and rotated which seemed at first to do the trick but was not the case. I suspected the new reman’ed trans next since the original ujoints were replaced at 135k with Moog units and they seemed nice and tight upon inspection.

I downloaded an app on my phone called Accelerometer Meter to help narrow down where to look. The app has a Spectrum analyzer that will save a snapshot of the amplitude of x,y and z axis of your phone’s accelerometer across several frequencies. My phone fit tightly in the center console lid cavity\depression(you'll want your phone firmly attached to your vehicle to sense the vibrations). I just ran the analyzer and got to where I could feel the vibration the worst with my phone lodged in that console cavity and hit the save button. The saved data will give you several frequencies and the their amplitudes in x,y and z. Look for higher values/spikes in any of those axis for the given freqs listed out. When saving the data, make note of your speed and trans gear and maybe engine speed. With that info you should be able to ballpark the speeds your wheels and from that use your rear end ratio to get your driveshaft speed. If you can find spikes in the saved data, you’ll just need to figure out what is spinning at that rate in rotations/sec to narrow down where to look.

On mine, it was a ujoint that the needle bearings were ground away. I found it this way but would have never suspected it from my inspection.

+1 I had something similar, it ended up being a U joint, the needle bearings had made a safe space for teach other in the bearing surface of the Joint, but only in one side of it.

A bad transmission could also cause something similar, or a rear end. But before jumping to conclusions you need to fill the gaps of when it started etcc.. as somebody already mentioned.