If your slide motor is like mine on my 28BHS, and I think it probably is, (sofa slide) look under the motor gear for a nut to turn with a socket and ratchet. It will be easier to see and do if you remove the trim piece that is just above the floor on the sofa. Only a few square head screws hold it in place. It will take quite a few turns of the wrench to move the slide in or out manually. I experimented with mine one time as I wanted to know the manual procedure which was not in the manual, nor was the location of the nut to turn.
2004 Chevy 2500HD Crew Cab 6.0l, 4.10r
2010 Jayco Jayflight 28BHS
Reese Strait Line with Dual Cam
P3 Brk controller