Ok ... just put in a new oil seal..

easy enough.. however when tightening the nut that holds the driveshaft flange - it locks the bearing up tight...

Is this like the old wheel bearings where you tighten them up till they feel stiff and then back off a quarter turn?

cheers

jon

Do you mean the propshaft flange ?

If so by tightening it up you have crushed the crush tube.
This subject has been covered many times in the forum. A new crush tube will be required plus a bit of care setting up the pinion pre-load.