Tasting is the only true way to tell. Lick it up directly from the floor to avoid contaminating it with cheeseburger grease on your fingers.
On a more serious note, check to see it it is gear oil is weeping from where a bracket was ground of during the rear end swap conversion. I had that happen to me on a 12 bolt. Gear oil will wick through the tiniest of passages.


1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission