[Ironangel]

Actually, shortening the front shaft doesn't change the DS angle because the carrier bearing is in the same location. The fact that you went from rubber to polyurethane mounts may contribute to your feeling something now that you didn't with the rubber mounts. Also, did you have both shafts with the carrier bearing balanced when the shaft was shortened? I dont think any of the changes you've made would affect the
pinion angle enough to cause a vibration. On page 4-24 of the service manual it describes rotating the rear shaft 4 splines to the left side of the vehicle. Model CE31403 rotates only two splines to the left. That phases the rear shaft to the front shaft regardless of the pinion yoke position. You should have both front and rear shafts with the (preferably new) carrier bearing balanced assembled together with new u-joints at a DS shop.