Could be the u joints in the front drive shaft. I work in a drivetrain shop. We retube, and use a single u joint weld yoke, along with a drive flange to replace the cv. This works very well if the truck hasnt been lifted.
Also check for slop in the slip yoke, if it isnt too bad, many times if you remove the boot, and grease the splines, it will help. The slip yoke and spline only go together one way, so dont force it back together!
It is cheaper to do the single u joint conversion than do a proper rebuild on the cv, if it is even rebuildable. If it isnt rebuildable, and your truck has been lifted, then expect to drop about $350.00 to replace the cv unit alone...
We do about 20 of these conversions a month for Dodges alone.