My truck has a shake for about a second when I hit bumps. The speed doesn't seem to matter. The u-joints have 20,000 miles. The mid-ship bearing (it's a SC long bed) was new at the same time. The carrier bearings were new 30,000 miles ago, but I did not change the pinion bearings. The diff. is quiet, except when it is cold out. Then it only makes a slight noise for the first few miles. The shocks (NAPA's best, kinda stiff) have about 10,000 miles. I plan on pulling the driveshaft and having balanced and changing the pinion bearings. Recent posts on this site make me think that I should also replace the tailshaft bushing. I know Ford does not service the bushing, you have to buy the housing assembly It is not leaking but I can feel some slop. When I leave work, I drive 10 miles down a highway, stop, and make a left turn. Some times I here a grumbling during that turn. It's the only time I hear it. Do you guys have any thought or suggestions?

Thanks