Lots of motorhomes had that setup. The one I owned didn't have the regular parking pawl inside the transmission to lock the driveshaft. It had a big drum brake on the back of the transmission, applied by a heavy spring. An electric motor with a worm gear drive retracted the spring when the transmission was moved into gear.
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!