Drive shafts out of phase

[Trevor]

I just replaced the u-joints on the front prop-shaft of the Defender. I don't know why I didn't notice it before but the shaft is out of phase, and it appears to be that way on purpose as the spline is pinned to prevent putting it in phase.

Now, I am guessing that it's designed this way or I should be feeling a lot more vibration than is normal in a Defender (sure, I know, that's a relative thing because they're loud and shaky at the best of times :->). My D2 isn't here or I'd check it too and compare. First I've ever seen a drive shaft purposely designed to be out of phase. Anyone know the backstory to why it is done this way?

[Trevor]

ok, just figured it out, so shortest thread ever.

The shaft is out of phase because the front diff pinion points upwards at the t-case rather than being in line....like every other vehicle on the planet. Someone decided to be different I guess :).

Since the horizontal is off between the two flanges the u-joints need to run out of phase to offset and prevent vibrating you off the road.

Clear like mud!

[Red90]

Because of the motion of the radius arms it works best to have it pointing at the transfer case. If it wasn't then the angles become poor through the range of travel. It has worked fine since 1969.

This is why disco 2s went to a DC joint at the t case. It reduces vibrations. The downside is the centering balls never last long.

[Trevor]

Good info, thanks John. Interesting design choice to be sure.