installed 8.25 from a 1997 inplace of a d35 under a 1990 xj. reused stock driveshaft as the one from the 8.25 seemed to short. i know have a knock that was not there before swap coming from front u-joint/tcase area.
4.5" lift on xj, but no noises before...no sye or tc drop
new u-joints
i did not mark alignment of driveshaft before removing........my haste

 

you have to better describe the knock. It it at start up or coming to a stop, relative to rpm or speed?