This comes from Doug. And it's one of the few unlicensed shirts I'll allow.
Tell me you weren't a fan of Najeh Davenport (at least briefly) and I'll call you a liar. He produced on a small scale during his time in Pittsburgh, and his backstory about crapping in a girl's hamper or closet or something is just legendary. He came after Jerome "The Bus" Bettis, so the Dump Truck nickname fit.
Doug used that nickname for an awesome shirt, seen above. He says he managed to sell a couple of these badboys.
I think I like it because the Black and Gold makes the truck look like a Tonka truck, and I had a black and gold Tonka dump truck when I was a kid. Gosh, I loved that thing. I'd take it out in my mom's garden and play in the dirt.
This is how you create good unlicensed shirts, people. Don't subtly imply that it's a Steelers shirt by using the words PITTSBURGH, STEEL, WORLD CHAMPS or any of that noise. Focus on who or what the shirt is really about, and let it ride.