4l60e Leak

[wreedZ71]

OK guys heres the story. Truck is 97 Suburban 5.7l 4l60e 204000 miles

 

Trans and TQ was replaced at Chevy dealer about 1 year ago, and flused about 6 months ago by local mechanic. Dad has been driving the truck back and forth to work since then, never any hard driving. Everything just fine. I drove the truck a couple days ago and parked on a very steep driveway incline with the parking brake. I noticed a very big puddle of trans fluid under the truck when I go to leave. Get truck on flat ground and check the trans fluid several times while engine warm and always read a little bit over the top of the hashmarks. I proceed to drive home 20 miles no problem.

 

Next morning on flat gound in drive way, no leaks, checked fluid and still appears a little high to me. Havent done anything to it. Dad has driven everyday since and appears totally normal to him. Hasent leaked anything either.

 

What could have caused this? Was it overfilled by mechanic when flush occured and the incline finally caused it to run out?