I had a strange issue this morning temp is around 30 here in the northwest I plugged the block heater in last night and awoke to a puddle of aft from the tranny leaking from the bell housing. I drove to the job site the truck sat for 6 hours and never leaked a drop. When I replaced the cab on this truck I ripped the shift boot a bit so I know there is decent venting of the tranny. I just don't know why the tranny would build pressure and leak. At 120 with the block heater but not at 220 after running.