Ok people, an update which basically confirms what I've been saying all along. I popped the pin at the front differential u joint coupling (actually there was a wire through the roll pin holding it in place and it came out when I removed the wire), splines seem ok but worn a bit. Can turn differential pinion shaft by hand completely in both directions no sounds. Guess we're into bigger job opening up front differential. i haven't attempted to drain oil if any in the differential, that will be next. I'll report back.