Join Date: Aug 2017
Location: Edmonton, Alberta Canada
Own a Commander?: Yes
Model year: 2006
Trim Package: Limited
Power-Train: 5.7L V-8 Hemi
If 4WD - system: QD-II
Current Mileage: 142,000 km
Hey bud, welcome to this forum. Lot's of good people here.
Did you just buy it or have you owned it since new?
A highway speed vibration is most likely the rear driveshaft. A tire imbalance is usually constant but can peak at a certain speed. You can also check motor and transmission mounts for damage. Does the engine run smooth?
If you can safely place it up on jack stands, you can have someone put it in gear while you watch the shaft for woble. I just did this for my own Commander. I set the front down on the subframe and had hydraulic jacks under the front control arms. The wobble in my rear shaft was huge.
I haven't noticed a huge vibration yet but the rear u joint on my shaft is definitely bad. I am working on making it serviceable.