Copyright Goodheart-Willcox Co., Inc. Heavy Equipment Power Trains and Systems 828 hydraulic steering motor rotates clockwise, it causes the steering cross shaft to rotate counterclockwise. The steering cross shaft drives the reverse idler clockwise, which then drives the left sun gear counterclockwise. The steering motor also drives a pair of external- tooth gears, similar to a cluster gear, counterclockwise. The cluster gear drives the right sun gear clockwise. If the hydraulic steering motor is the only input into the steering dif- ferential, the tractor will counter rotate. The planetary ring gears are the right and left output members of the steering differ- ential. The ring gears directly drive the final drive sun gears, which are the inputs to the right and left inboard single-reduction final drives. The original 8000T tractors through the 8030T series tractors, however, have outboard single-reduction final drives. See Figure 24-21. Komatsu Hydrostatic Steering System Komatsu manufactures a dozer that uses a differential steering system that is labeled as a hydrostatic steering system (HSS). The Komatsu hydrostatic steering system and the differential steering system in John Deere twin rubber track tractors have a similar design, in that the pinion and ring bevel gear set drives a bevel gear shaft, which drives both plan- etary carriers. The hydraulic steering motor also controls the steering planetary sun gears. On the D275AX-5 Komatsu dozer, the largest Komatsu differential-steered dozer, the left and right service brakes can be used as steering brakes if the operator actuates a turn mode switch. The right or left brake is applied when the differential steering is unable to make the dozer complete a tight turn. See Figure 24-22. The hydraulic steering motor drives a pinion gear that meshes with gear A, which is in mesh with gear B and gear C. Gear C is connected to the same shaft that has gear D on its opposite end. Gear D is in mesh with gear E. Gears B and E are coupled to the left and right sun gears respectively. If, for example, the operator steers the dozer to the right, the hydraulic steering motor and its pinion gear rotate clockwise. The pinion gear causes gear A to rotate counterclock- wise. Gear A drives gear B, gear C, the transfer shaft, and gear D clockwise. Gear D rotates gear E counterclockwise. This power flow through the gears ends with the left sun gear rotating clockwise and the right sun gear rotating counterclockwise to power their respec- tive planetary carriers and final drives to turn the machine to the right. Outboard single-reduction final drives Closed-loop hydraulic steering motor Closed-loop hydraulic steering pump Goodheart-Willcox Publisher Figure 24-21. This differential steering axle is used on John Deere 8000T–8030T series tractors. Note the outboard final drives and the hydraulic steering motor. The dedicated closed- loop hydraulic pump and motor provide input to the axle anytime the tractor is steering. Later-model John Deere 8RT tractors use inboard planetary final drives, which provide a more accessible drive axle for easier repositioning of the tracks when their spacing needs to be changed.