Frankly, I would be concerned if my ZF was NOT leaking!
But more than likely you need new seals 805 & 806 in the illustration. Can be replaced with no major surgery.
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.