Update: took my car to another dealer for a second opinion. The technician acknowledged the tranny noise and conceded that it might not be normal. He wanted to do some research and drive another '13 GT before he passed judgment (which will happen next week).
I appreciate the dealer's willingness to look into the problem, but I suspect that I'm a long way from closure. In the interim, I have a noisy transmission that shifts smoothly.
2013 Deep Impact Blue GT Premium, MT82, Comfort,
Electronics, 3.73 gears, Ford Racing Strut Brace,
Boss 302S 19" wheels,
255-40-19 Michelin Pilot Super Sports,
Bama 91 Octane Race Tune