Thanks for the links Ken. They will come in handy. Nothing worse than a 123 that has the shakes. I checked the drive shaft and it was all ok (I now have a couple of flex discs to get rid of). While I had it on the lift I noticed the left axle shaft had some veritcal movement to it while spinning the wheel. So I then checked the right side, all was well except that there was some grinding and clunking. All four boots are either leaking or about to be so I decided to change both axles. It is going to kill my wallet but I can't let my ride have the shakes.
2006 E350 98K miles
2013 Ford Explorer 15K miles