Driveshaft alignment

No arrows on the driveshaft. Put it back together with new u joints 

Thanks! I’m on it!

Actually, there are sixteen splines on the driveshaft and the yoke could be installed in any of those ways. There are only two choices where the correct phasing will be evident.

My attempt to explain phasing of a driveshaft was perhaps not involved enough. Yes, the slip yoke can go on multiple ways, but only two ways yield a correctly phased driveshaft. If a driveshaft has been dynamically balanced, there is only one way that the driveshaft will probably operate without vibration; that is if the yoke and spline stub are installed together just the way it left the balance machine. A 180 degree phasing may or may not yield a satisfactory vibration free operation depending on how lop-sided the slip yoke is.

The lower photograph that I showed in the above post illustrates the most common phasing mistake made while installing a driveshaft. Any other of the possible ways that a slip yoke could be installed on the spline except as illustrated in the top picture is out of phase and could possibly introduce vibrations into the driveline under operation.

There are extreme industrial applications that involve severe driveshaft angles where the driveshafts are purposefully designed out of phase to cancel bad harmonic vibrations but those are exceedingly rare. To my knowledge Jeep never used a factory installation of an out of phase driveshaft. If an out of phase driveshaft is going to cause a vibration problem it will more than likely be the rear driveshaft because of the angle the driveshaft has to operate at. Front driveshafts in a flatfender usually don't cause vibration problems even if they are out of phase because the angle is shallower, unless the splines and yoke are worn out or one or both of the u-joints is worn or binding.

Full disclosure: I built or repaired hundreds of driveshafts during a 18 year period where I owned and operated a shop that also repaired truck transmissions of all sizes, transfer cases, axles, and power take-off gearboxes and shafts. I closed the shop in 1995.