Front drive shaft vibrating

When I disconnect the front DS I have no vibs. With front DS connected and in fulltime 4wd I have no vibs. But when in 2WD I have vibs at about 50mph up. All the unis looks good. The slip joint has a slight movement in it, I dont know just how tight it should be. I am at 5.5" and have a double cardan DS in the rear but the rear is fine. The lift kit is a 4.5" RE kit. I am about to have the bushes checked in the diff where the control arms mount. Any ideas?

How's the pinion angle? If you have adjustable controls arms you might try changing the angle and see how it is affected. Also, you might not have enough spline length engaged on the driveshaft.

Good luck.

Just from eye the pinion angle apears to be zero. I have all fixed length arms.

Maybe the driveshaft is out of balance. Try removing and rotating it 180 degrees at the pinion. Just an idea.

Brad

The length looks good. I have had the front shaft in the back and it ran perfectly as it does in the front in full time 4WD so I doubt it is a balance problem.

How much play in the slip yoke is normal?

I rotated it 180 degrees and it seems to have fixed the vibration???