Thanks for the replies. That's the answer I was looking for. Everything on the web about driveline vibration never describes the speeds it starts at. The tires had been sitting for 3 years on a f-150 before I put them on the cherokee. The vibration seems less now than it did when I first put them on. Now they just seem like loud mud terrains. Still not as bad as my unbalanced 33" super swampers I had on my s-10.

99 Sportage 2Dr, 1.5" body lift, 30x9.50 Cooper M/T's, high lift, CB, custom bumpers, Warn manual hubs, Tom Tom GPS, snorkel.
99 Jeep Cherokee 3" lift, 31" mud terrains