what addams says is correct, sometimes these sensor wires at the motors can be damaged from debris getting thrown up inside that comapartment and if they do disconnect for any reason it will slow down or even disable the truck drive.
but having a serial number will still be needed to make sure you get the wires connected correctly, there are color codes on each wire and they did change at some point in the newer models to some different colors.
If the dataplate is missing just look along side of the battery compartment on the frame and the serial number should be stamped in the frame there. Most of the cat trucks did have 2 dataplates though, one on the hood and the other located on the front frame between the mast and truck frame.