Optional SCU Internal Valves . . . 634
Inlet Check Valve . . . . . . . . . . . . . . . . . . . . . . 634
Inlet Relief Valve . . . . . . . . . . . . . . . . . . . . . . . 634
Load-Sensing Relief Valve . . . . . . . . . . . . . . . . . . . 635
Cylinder Port Relief Valves . . . . . . . . . . . . . . . . . . . 635
Anti-Cavitation Check Valves . . . . . . . . . . . . . . . . . . 637
SCU Features . . . 637
Non-Load Reaction. . . . . . . . . . . . . . . . . . . . . . 637
Load Reaction. . . . . . . . . . . . . . . . . . . . . . . . 638
Wide-Angle Steering . . . . . . . . . . . . . . . . . . . . . 638
Cylinder Dampening . . . . . . . . . . . . . . . . . . . . . 639
Q-Amp Steering . . . . . . . . . . . . . . . . . . . . . . . 639
Traditional Steering Priority Valves . . . 640
Steering Priority Valve Operation with the SCU in Neutral . . . . . . . 640
Steering Priority Valve Operation with the SCU Steering Left or Right . . 640
Steering Priority Valve Load-Sensing Relief . . . . . . . . . . . . 641
Load-Sensing Line . . . . . . . . . . . . . . . . . . . . . . 641
Diagnosing Steering Systems . . . 642
Electronic Steering Features . . . 644
John Deere ActiveCommand Steering™. . . . . . . . . . . . . . 644
Caterpillar Quick Steer . . . . . . . . . . . . . . . . . . . . 644
Case IH 4WD Combination Steering . . . 645
Image Credits 651
Glossary 652
Index 666
xxv