Front driveshaft vibes

98xj AW4 NP231 3" lift+ 3/4" spacers

I recently made a trip across the country, and for about half the way, I had bad vibrations around 70mph. Had the tires balanced, and there was no change. So I took the front DS out and it drives smooth to well over 75. I did notice my front pinion seal is leaking (has been for years) and the slip yoke on the shaft has some play.

Is it common for these shafts to go bad? Or could my pinion bearing be causing the vibrations?

The Centering ball does occasionally develop play and needs to be replaced. I would check for any slop in the slip joint as well while you have it out. Any slop in either will lead to some bad vibes and cause premature failure of t-case seals and bearings and/or pinion seals.

I just replaced all 3 u-joints and the centering yoke about a year ago. I think I'll just pick up a new shaft from a junkyard and see if it works.