pinging noise from driveshaft/tranny?

Did you see any score marks on the DS? You can use a real light guide-coat of paint on a DS (in the spots you think might be rubbing). Take it for a drive till you hear the noise and then check it to see if the paint is scored off anywhere. The E-brake bracket and mufflers are places that can rub, especially on off-camber turns.

Good luck.