847alexc

Hmm... I have a couple of thoughts:

1) Was the speed sensor/computer reprogrammed for those big tires? If not the transmission would be upshifting too soon, causing that sort of shutter, which is not good for the clutches either. Check the speedo against a friends car driving next to you.

2) Are the tires properly balanced? Often those large tires can be tough to get balanced properly causing a distinct shimmy and improper wear.

3) alignment issues related to the lift, was the vehicle realigned after being jacked up. A tire shop could check balance and alignment at the same time easy.

4) Finally, however unlikely at 15k, drive shaft issues. Speed dependent shutters are often caused by bad u-joints (unlikely at 15k) or improperly balanced rear drive shaft (more common from factory). The latter is more difficult to diagnose, check 1-3 first.