I'm looking for some of that seasoned experience I've seen before. I'm addressing a problem I posted about 6 months ago that is unchanged. I've got an '04 SC 150 (4.6L) that I've had vibration issues with since day one. I've had the tires replaced time and again, road force balanced, the counter-balance placed on the drive shaft, the drive shaft itself replaced, the ring and pinion replaced and the dampening system put on the truck. None of it did a thing for me. I've had two guys recently tell me that my problem is a design issue in the two-piece drive shaft and its offset. Both suggest that the harmonic imbalance at certain speeds, in my case, also approx 50 mph, is the problem. Both suggest that the problem can be fixed by buying an aftermarket driveshaft, one piece. I've had it with the problem and am willing to try it, provided it's valid and worth the investment. Any insight from anyone out there regarding this issue is appreciated.