Originally Posted by costina

New halfshaft bearings fitted correctly and fully cleaned axle tubes and some sealer around will resolve this issue.

Hardest job is to get the bearings off the actual diff. Make sure all shims remain on the same sides. Fit new bearings.
Pinion is also easy to remove but you will need a new crush washer. Pinion needs to be torqued up to spec. Any cortina/capri haynes manual will have specs for torques.
Refit diff and check for backlash and teeth contact using engineers blue.
Should be all ok if not it will require removal of bearings and adjust shims to suit which can be tricky.
Search for lea123 on turbosport he can do them if you don't fancy it. Also many trnasmission place will do it.