Drive shaft issue.
I have an '02 4 door long bed 4WD. I just replaced the ujoints with my press and now it vibrates at 45 and 60mph. First I thought it was the now greasable ujoints that are throwing it off but every one in town says I'm crazy. the slip joint in the shaft has a little play, when putting it back together I put some heavy grease on the splines where my friend at Napa says ford uses wax on the splines. Should I find some shaft wax or should I start looking for a gently used shaft or get a new one?