Sharkbite 928

my 5 spd 78' had the tranny rebuilt just before I bought it 1 1/2 years ago. I travelled all over for the last 2 years and although I saw spots on the rear of the body I did not know what was causing it . I did tell my mechanic about it several times in the past. Well now I am home and I found that the leak is coming from the breather mushroom on top of the differential. It has leaked only about a quart in 10,000 miles and we refilled it, but wonder why it is as they call it "sweating" If need be we will bring it back to the tranny shop but was wondering if anyone had thoughts on this? I also want to thank the Michigan Chapter of 928ers for turning me on to this site and it was a pleasure to meet a great group of shark enthusists The site has been informative and helped me to understand some of the issues I have had to deal with a car I feel I cannot live without . Are there any people who share this desire in So FL? If so I would like to meet if possible. Contact me if you like