2005 chevy trailblazer

Engine starts and runs good.     Was driving in town
when this happened.  So I drove interstate for 35
minutes no problem.   Ran and shifted like a champ.  
Got into town and stopped in to a muffler shop to get a
quote shut off and restart just perfectly.   Reverse and
back to drive to get into the muffler shop Reverse and
drive to get out of shop just fine.    Drive down the road
2 miles hit a red light.   That's when it happend.  No
sound.  So feeling. No nothing.  It feels as if it's in
neutral throughout the PRNDL  but "grinds" going back
to park.     Solenoid??   Fluid is good and clean.