Where exactly is the drip? From the rear of the case cover coming through the bolt holes? typical place to seep from. Penn Grade is a conventional gear oil so you are fine there.
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.