[gonecheenin]

Does your front shaft have a CV at the front axle or a standard u-joint?

If its a standard U-joint and your shaft is in good shape mechanically (no worn slip splines or anything damaged/out of balance) thats were your vibration is from

First off:
Any U-joint running at an angle makes a vibration
2 U-joints running at the same angle on the same shaft make 2 equal vibrations which cancel each other out

The Grand's stock Spicer style CV at the T-case has two U-joints in it which cancel their own vibrations, so when you lift the Jeep & the axle side u-joint starts running at an angle you now have a vibration that isn't being cancelled


Only six choices to fix your issue;

1) lose some caster to improve pinion angle & help reduce the vibration
2) install an XJ/MJ HP30 front diff to improve pinion angle
3) have front end cut & rotated to improve pinion angle
4) install a standard 2 joint shaft (like a YJ) so you can more closely match your axle side joint angle to the T-case side joint angle
5) have a custom front shaft made with two Spicer style CV's in it
6) run without front shaft

Personally I go with either #2 or #4 on my ZJ's