Vibration at 73 MPH

Have a 2003 Silverado 2500 HD 4X4 Ext. Cab, 6.0 liter with Automatic.

When truck hits 72 - 73 mph the four wheel drive lever vibrates. Dealer has replaced two rims and three tires. Swap out rear drive shaft. Truck still vibrates and dealer has know answer. Purcahsed the truck new and problem started within the first couple of hundred mile, now has 2800 miles.

Please help!

I have a 97 Chevy that had a similar problem. But my truck vibrated at all speeds. I went through two sets of rims, 3 sets of tires, had my drive shaft balanced and much more. In other words a bunch on money for nothing. Here is what solved my problem. Find a tire dealer that has a Hunter GSP 9700. This machine is the next generation of tire balance machines. It measures the high spot on the rim, then the tire. The assembly is broken down and the hight sopt on the rim and the high sopt on the tire are set oppsite of each other. The tire is reinflated and placed back on the machine. As the tire is spinning a cylinder is lowered onto to tire to simulate the tire being driven on the road. At that point the machine records the high sopt on the tire and balances the tire. My tire shop only charged me 27.95 the cost of a normal balance. I still feel a little road vibration but over all it is a 99.995% increase. On some roads I dont even feel teh vibration. You may want to drop a couple of p.s.i. in each tire. My tires call for 35 and I an running 33. Let me know if this helps you.