Pump seal is most like not to leak at rest, there is drain back passage behind it and with no pressure at rest the area behind the seal will drain below the level of the seal. I do not believe the drain back is clogged/restricted as that would show a leak while running as it would be unable to relieve the pressure properly. There would also be a noticeable trail of fluid running down the pump. Now the o-ring how ever can leak at rest as the converter drains off during rest the level in the trans can rise above the bottom of the pump bore and seep past the o-ring. With more and more of our parts being made abroad the quailty is getting worse, I have seen seal and O-ring come in that were not completly molded. I would replace that as well as putting sealer on the threads of the bolts at 5 and 6 o'clock in the pump.
