Gasket or o-ring?

[autopilot]

On my '98 TD...at the rear 4-bolt square flange of the drive shaft tube, where it bolts to the differential housing......Is there a gasket or O-ring for that? I've noticed the bottom of that bolted connection has been black & greasy the last few times I cleaned the bike up. (not a lot, but it's obvious that it's there) I can't really get where I can see around under the bike generally. Had it checked, bolts are tight. Fluid levels are good. Is it possible it's coming from somewhere else. If so, where might that be?

[Squeeze]

There's no Seal at all.

 

The only Way i can see little Oil there is when the Oil Seal on the Drive Shaft isn't the best anymore and lets a Drip of Oil go through.

 

 

If it doesn't increase, nothing to worry about.