U-joint or CV joint? This decision is based more on the angles under your 4x4 than personal preference. If the pinion angle and the angle at the transfer case aren't exactly the same, you're likely to get driveshaft vibration using U-joints at both ends of the shaft. A CV joint will overcome this, but a CV joint can't work with as great an angle as a U-joint of the same size. Remember that the U-joint angle must be checked with the axle dangling at full suspension droop as well as when the 4x4 is sitting on level ground. Bringhurst's final note on U-joints is that he prefers to use Spicer nongreasable types. These have proven durability and are sealed to keep mud and water out.