I have a 2010 Jayco and the manual crank is behind the cardboard underbelly. you will probably have to remove that to see it.. mine is on the opposite side of the trailer as the slide. It is the full width of the trailer so mine is not under the slide but on the other side of the trailer.
2010 Jayco G2 32BHDS
2003 GMC Duramax Crew Cab