The Gators (3-6, 3-5) will finish with a losing SEC record for only the third time since 1992.
And in a common theme this season, South Carolina's defense came through.
Henderson fumbled the ball, and the Gamecocks recovered the ball and took it nearly to their 25-yard line.
Franks, who completed 10 of 25 passes for 174 yards, replaced starter Malik Zaire, who left in the second quarter with a leg injury.
The Gamecocks scored a TD in the third quarter.
The Gators cut South Carolina's lead to 28-20 with 3:43 remaining on a 1-yard run by Mark Thompson.
Florida: Unless the Gators pick up a game on December 2 to replace the one cancelled for Hurricane Irma and win out, they won't make a bowl for only the third time in 31 seasons. Five of them have come in the past two games ...
The only problem for SC was turnovers as QB Jake Bentley threw three interceptions on the afternoon.