If it,s an auto trans. it could have a leak in the cooler. Other then that, with the original type 6 cyl. it would be very rare. Being you just got it I would flush it out real good & refill it & see what happens. It could have gotten put in by mistake. If it has the later model 6 cyl. (63 up) they are noted to crack in the lifter gallery & cause that.
