This subject did come up some time ago and the idea was to rotate the bar that runs between the geared rollers. Probably have to use something like a open-end wrench to do it and bring your lunch down there with you. May even help to have someone pushing against the slide as you crank it. There is no manual crank rod/port to do that on our models.
Another possible method may be to rig a come-along strap between the end of the slide hardware and the frame and pull it in that way.
If it's not a ram failure or leak and maybe just the hydraulic pump motor, then you only need to remove the cover on the end of the motor, insert a 1/4" hex bit into the orifice and drive it with an electric drill. May need an extension to reach it from inside the basement, but that technique is covered in the Lippert manual on hydraulic slides. Just in case, I have the fittings to do that in my toolbox.