Sunseeker 3170DS manual slide extension?

I need to replace the rear motor of my giant slideout which is currently retracted. I took apart the inside of the unit to access the motor, which I found, but it appears that it must be released and replaced from the outside.

But I can't extend the slideout... and can't figure out how to do it manually. I've tried removing power and control wires from both motors. I don't appear to have any type of 5/8 inch manual system...

Any thoughts?