Variable Hydrostatic Drive Motor Applications . . . 584
Two-Speed Motor Applications . . . . . . . . . . . . . . . . . 584
Infinitely-Variable Motor Applications . . . . . . . . . . . . . . . 588
Variability by Using One or Two Variable-Displacement Motors . . . . . 589
Single-Speed, Fixed-Displacement Hydrostatic Motor . . . . . . . . 591
Additional Hydrostatic Valving . . . 592
Inching Valve . . . . . . . . . . . . . . . . . . . . . . . . 592
Manual Bypass Valve . . . . . . . . . . . . . . . . . . . . . 594
Electronic Pressure Release Solenoid . . . . . . . . . . . . . . 595
Internal Pressure Override . . . . . . . . . . . . . . . . . . . 595
Pressure Cutoff Valve . . . . . . . . . . . . . . . . . . . . . 596
Electronic Anti-Stall Control . . . . . . . . . . . . . . . . . . 597
Electronically Controlled Displacement . . . . . . . . . . . . . . 598
Accumulator Effect . . . 598
Chapter 24
Hydrostatic Drive Service and Diagnostics
603
Centering Adjustments . . . 603
Single-Servo Cradle Bearing Pump . . . . . . . . . . . . . . . 604
Dual-Servo Trunion Bearing Pump Adjustments. . . . . . . . . . . 609
Shaft Run-Out . . . 610
Startup (Commissioning) of a Hydrostatic Drive . . . 611
Hydrostatic Drive Diagnostics by Symptom . . . 612
Overheating . . . . . . . . . . . . . . . . . . . . . . . . 612
Creeping Hydrostatic Transmission. . . . . . . . . . . . . . . . 615
Low Power or Sluggish in Forward and Reverse . . . . . . . . . . 615
Low Power or Sluggish in Just One Direction. . . . . . . . . . . . 618
Coasting or Freewheeling Transmission . . . . . . . . . . . . . . 620
Transmission Will Not Move in Either Direction . . . . . . . . . . . 620
Effects of the Directional Control Valve Orifice . . . . . . . . . . . 621
Charge Pressure Is Too High . . . . . . . . . . . . . . . . . . 621
Do Not Attempt to Isolate a Hydrostatic Pump . . . 621
Using a Hydrostatic Transmission Test Stand . . . 622
Chapter 25
Steering 627
Steering Control Units . . . 627
SCU Components Design, and Operation . . . 628
Open-Center SCU . . . . . . . . . . . . . . . . . . . . . . 630
Closed-Center Non-Load-Sensing SCU . . . . . . . . . . . . . . 630
Closed-Center Load-Sensing SCU. . . . . . . . . . . . . . . . 631
SCU Neutral Operation . . . . . . . . . . . . . . . . . . . . 632
SCU Left or Right Steering Mode of Operation . . . . . . . . . . . 632
SCU Dead Engine Steering Mode . . . . . . . . . . . . . . . . 633
xxiv
