Bearfoot2 may have hit on the answer for you. It could easily be your tranni shifting into 1st just as you stop. If that is the case I do not think it is a problem, but others may have other thoughts on this.

 

pull ur drive shaft out and put some grease in the yoke and see if that takes car of ur problem.

Dan

 

I don't think it has necessarly shot your theory of the drive line splines being shot. All it has done is isolated the problem between driveline and suspension (the rest of the truck)
What you have is a drive line issue, which could be as simple as Bearfoot has stated, the tranny shifting into first. Or as you have noted the splines are worn on the drive shaft and the shaft needs replacing.
How are they worn?
can you grab the two "halfs" and have them twist in opposite directions? or at the spline can you grab the shaft and lift it up and down?
I think what you need to do next is take the drive shaft off the tranny and check to see if the splines bind in *ANY* way do this before you grease it. you will really have to be creative in the way you slide the splines in and out, put pressure (imitate a tranny) and slide splines in.
If your drive shaft checks out ok then your tranny may not be set up right. I won't even guess at how to trouble shoot that one, or what could be wrong. I repair telephones for a living

 

OK, thanks guys. Right now the truck is in having the valves adjustment and the timing checked, but when I get the truck back I will look into the drive line more thoroughly.