Outer Limits 4x4 Board

Lifted a '92 sierra standard track 60mm. Straight away got a vibration that smoothes out the faster you drive. Only does it in 4wd. We have taken out the rear driveshaft and still does it. The problem must be in the front. Diff has just been rebuilt and all new uni joints. We have rotated the driveshaft and it doesn't affect the vibration. Driveshaft angle is ok. Anybody got any sugestions? Could the transfer case cause any drive line vibration?

Steering dampner, wheels out of balance (try rotating them rear to front)
Is it a vibration through the steering wheel or through the driveline/g-box ?
Did you replace the unis on the short jackshaft between g/box and transfer ?
What are the joints/rods like on your steering setup, mine are quite worn with the rubber boots torn and i get a decent vibration and occasional clunking with small tyres on. Not as bad with larger ones.

If the lift is a bodylift then you may need a spacer on your steering shaft or it may just need to be loosened then tightened once its adjusted itself.

im presuming its a suspension lift?

Driveshaft angle is ok

-as in looks ok or have you actually measured the angles? the sierra transfer tilts backwards so it doesn't take much lift to bugger the front shaft angles up
-short jackshaft between gbox and transfer?
-front wheel bearings?
-wheel balance?

Sorry, it's a suspension lift.

There a new uni joints in the jackshaft and both driveshafts.
Front diff has been completely overhauled, so new wheel bearings, swivel bearings, carrier bearings etc.
Steering damper is brand new.
Tyres have been on and off several times so are unlikely to be in their original position.

All of that was done after the vibration appeared.

The driveshaft angle 'looks' ok. it is a straight line through the diff pinion. I have bought some castor wedges and will probably get those in this w/end. Can the transfer be tilted to correct the alignment at that end?

Rotating the transfer is not really an option, not only will you have to mod mounts, but it will throw off youre input and rear drives.
You havent mentioned if you have checked that the jackshaft is in phase, because if theyre not, that produces vibrations.

what do you mean by in phase PJ?

also if you have pull the two halves of the front shaft apart and replaced them not in alignment this may cause vibrations as well. there should be two dots to line up on the splined shaft and yoke so the unis are both in alignment.

also - if the pinion is point straight up at the tcase the angle is wrong... unless you're running a double cardan joint?