45 tonners were designed for industrial use, so use smaller (or less) components that 44-tonners, which were meant for road service. 45-tonners get most of their weight from a very thick deckplate. Also, 45-tonners have only two traction motors; the other axle on each truck was powered via side rods or a chain drive inside the truck frame. I find that many people call any GE centercab a "44-tonner," but industrial-use models included 43, 45, 50, 65, and 80-tonners (and on up to 144-tonners), and there were often several variants of each model. Good references include Kalmbach's "Second Diesel Spotter's Guide" and Jay Reed's "Critters, Dinkies and Centercabs."