Here's another "guess at what you have"....
From the photos, it looks like a HappyJack slide system. It's not a "through the frame" design, but rather a "in the frame" design. The motor is mounted "inside the slide assembly" rather than "in the frame, beside the slide assembly" as it is in other designs...
There's a picture of the slide mechanism on the HappyJack website. It shows how and where the motor is mounted. My guess is, based on the design of the gear teeth in the slide ram photo that you posted, the motor is mounted to the front of the slide assembly, directly bolted to the forward ram, under the slide floor, but above the trailer floor and well above the coroplast. You might be able to see the motor by lifting the carpet skirt on the slide and using a flashlight to shine under the slide/above the trailer floor.
Here's the link to that picture:
https://happijac.com/2011-08-15-13-57-08.html