Was it the drivers or passenger side cv joint.Ok, after calling Marty at Raxles to order the new one and thinking about why this mystified me, I think I've figured it out.
Most of the threads I found about drivetrain vibrations that ended up being a bad axle talked about vibrations at all rpm, including idle. Mine only did it at specific rpm's and under specific loads and the difference was what confused me.
I went back and re-read some of the threads and realized that every one of them was dealing with a slush-box, not a 5-speed. Once that little bolt from the blue struck, the problem became very clear... :banghead: