just bought a 2010 tundra, 4.6l 4x4, at about 55 mph the truck seems to shake or vibrate a little, tires or transmission? the tach holds steady, doesnt feel like its slipping. no jerk on take off or stop, bought it with 8 miles on the truck, now i am wondering if i made a good choice. any ideas would be helpful, dont want to take it back if its something stupid. like me.