Running the gears backwards can be a bit noisy. I've driven 3-speed auxiliary transmissions on big rigs that made a racket, but they pulled well for untold thousands of miles. Mount the second transmission in rubber-cushioned crossmembers to isolate most of the noise.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!