When you say 'near the relay', what relay do you mean? The one on the starter itself (solenoid)? If so, and it's the starter that's making this noise, then it sounds like the bendix is not 'jumping forward' to engage the starter to the flywheel. If you are referring to the starter solenoid on the passenger side of the inner fender, then I would try applying the 'start' signal straight to the starter and bypass that starter relay (if that makes sense, not 100% sure how the system works, but on another car I have, I can run a relatively modest wire from the battery straight to the solenoid on the starter, which will engage it, even with the ignition off, so that's how I test the starter working). Good luck, sorry if my advice is not correct for this truck.