gb38 The GB 38 gearbox is a transfer gearbox either left and/or right drive as required. The shafts are 20 tooth 1.75” PTO spline or 1.75” diameter ground. All gears and shafts are hardened and coupled together by involute splines. The ratio is 1:1 with a power rating of 120HP at 540 RPM. Housings are made of SG iron with gears and shafts made from alloy steel. Quality bearings and seals are used throughout.