If it is a new set-up(installed within the last 3-4yrs) the compression coupler at the housing is a bit of a PITA, too tight and you crush the rubber o-ring, too loose and it doesn't seal up correctly. Might remove the coupler at the diff and see what the o-ring looks. If the o-ring is bad, call ARBUSA and talk to the tech department, they will likely send you a new fitting at no charge.
