Tighten the top two nuts on the rear of the OD unit. There is normally a copper washer under them but over time the nuts work loose and the oil comes out from under the washer.

This is the most common area for leaks. Rarely between the OD case and the trans adaptor.

The gasket to the rear of the center metal ring can be replaced without removing the OD fromm the trans. The rear case just comes off.

IF the front gasket is leaking, the OD has to come off to replace the front gasket. To remove the brake ring,(metal band), the cone clcutch must be released and it is held by nuts accessable only after the OD is off the tranny.

If you take it off this far, replace the two O-rings on the actuating pistons. These should be considered a wear item and if accessable replaced "just because". A cost of about two dollars now will save you from pulling the OD later when it fails to engage at a later date.

Duane