I parked my truck on the ramps at an incline and overnight it leaked all of the trans fluid out through the yoke. I am sealing the seep hole up but think that something else is wrong for all of the fluid to come out this fast.

What would cause the fluid to pour out the tail shaft when the truck is on an incline?

The infamous air escape hole. GM put the hole there for venting as the sliding yoke moves up & down the output shaft.

The O-ring used to seal is broken or worn out inside the yoke.

The infamous air escape hole. GM put the hole there for venting as the sliding yoke moves up & down the output shaft.

The O-ring used to seal is broken or worn out inside the yoke.
Thanks, I'll look for this o-ring when I take off the tail shaft. Or will it stop dripping if I seal up the hole?

you could either pull tailshaft and replace oring. or seal up the yoke inside with silicone.