[cadillac_al]

I always say if the vibration goes away at a higher speed it is tire balance. It's pretty hard to get a good balance on truck tires. My 76 had a vibration right at 55 mph since I got it. I would just try to drive at 60 mph where the vibration goes away. I just bought new tires and they took a lot of weight to balance them. My vibration is now at a different speed but I can still speed up to make it go away. I can live with it.

Some shops have the old balancers that spin the wheel fast. With the new balancers you just spin the wheel by hand once or twice but they give a lot better balance. My truck got balanced with the old style balancer because that is where I bought the tires. If I was a little more OCD I would take them to another shop and get them balanced on a newer machine.