The F4W56A is a revised version of the F4W56L mounted on the B110 series. Modifications have been made on the following points to strengthen the gears and bearings, and to improve lubrication performance as well as noise and vibration proof at high-speed driving.

(1) Strengthened gears and bearings: Although there is no change in the gear ration, each gear has an increased width by 0.039 to 0.079 (1 to 2 mm) and the countershaft, front bearing and main shaft bearing are strengthened.

(2) Improved lubrication performance: To ensure proper lubrication in the rear extension bushing, an oil dam is installed in the center of the extension.