$35 Electric Power Steering with Fail-Safe - No eBay module and no caster issues!!!

Something is binding for sure. There are only a few wires (+ and -) and the 12v keyed wire. If the box is clicking, that is the relay firing up.

The first motor I got was infact bad. I tested it on the bench and it didn't freely move lock to lock. It had a hard spot in it. So went ahead and got another and it was good.

The fact that yours works with the wheels up, but notnwhen the wheels are down is interesting. What size tires? Not sure I've seen this mod done on a truck.