Amtrak’s second F40PH order incorporated several changes to the original Phase 1 design. Phase 2a and 2b units (230-279, 280-328) received larger 1800-gallon fuel tanks mounted toward the front of the frame. The air reservoirs were shifted toward the rear and to the engineer’s side, while the battery boxes were located on the fireman’s side. Newer and wider Nathan K5LA horns were specified, requiring a wider horn notch on the cab roof. Units 280-328 (termed Phase 2b) had four vertical ribs at the rear of each side.