Field reports on the RS-2 indicated a few weaknesses that resulted in the RS-3 design. The initial RS-3 specification, E-1662, included the Model 244D prime mover (now rated at 1600 hp), which addressed misalignment between bearing saddles and caps that had led to crankshaft and bearing failures in the earlier versions of the 244. Although the truck wheelbase remained the same, the RS-3 was 6 inches longer (55 feet, 11 inches) than the RS-2, as a result of changing the belt driven auxiliaries to gear drive. In addition, the fuel tank was removed from under the cab to below the frame between the trucks, which forced the batteries to the short hood running board, creating a raised section on both sides. The short hood was widened to allow a dynamic brake option, or a steam generator. In the rare case of a customer opting for both, the short hood was raised, creating what was termed a "hammerhead". The RS-3 was equipped with a GT581 main generator driving GE 752 traction motors, interchangeable with FA-FB locomotives, simplifying maintenance stocks. This photo illustrates a late production RS-3. When introduced, the RS-3 had three rows of louvers on the long hood engine compartment access doors next to the radiator intake, and three more next to the cab, no louvers in between (21 units). The next group built had small louvers added to the rest of the access doors, but only at the top and bottom, and the battery box louvers were rotated from vertical to horizontal. Finally, Alco replaced the louvers with two carbody filters on each side. Laboratory tests which introduced "standard Arizona road dust" into the air intake indicated that although the lube oil filters were trapping the dust pulled in through the louvers, damage was still done to piston rings and crankshaft bearings. A retrofit package to replace the louvers with filters was offered by Alco.