TURBOCHARGER GP 9Y9561 - Caterpillar

Cross Axle Differential (XAD) Lock System
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(23) Manifold supplying oil from the brake pump to the Pressure reducing valve for the XAD
(24) Front Cross Axle Differential (XAD) Lock Solenoid
(25) Center Cross Axle Differential (XAD) Lock Solenoid
(26) Rear Cross Axle Differential (XAD) Lock Solenoid
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(27) Wheel Speed Sensor (one on each wheel)
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Cross-axle differential lock system (differentials released)
(23) Manifold supplying oil from the brake pump to the Pressure reducing valve for the XAD
(24) Front Cross Axle Differential (XAD) Lock Solenoid
(25) Center Cross Axle Differential (XAD) Lock Solenoid
(26) Rear Cross Axle Differential (XAD) Lock Solenoid
(28) Brake, Fan, and Hoist Pump
(29) Front Cross-Axle Differential
(30) Center Cross-Axle Differential
(31) Rear Cross-Axle DifferentialIf the wheel speed sensors indicate wheel slippage from left to right on any given axle, the Chassis ECM will ENGAGE one or more of the Cross-Axle Differentials (XAD) to ensure that power is sent to the wheels that have the best traction. The schematic above shows the XAD clutches DISENGAGED on all three axles.Brake, fan, and hoist pump (28) draws oil from the main hydraulic tank and provides oil flow to combination valve (23). Some of the oil flow from combination valve (23) is used to operate the XAD system. The oil pressure to the XAD system is set at approximately 6000 kPa (870 psi) by a relief valve inside combination valve (23). Oil flows to front cross-axle differential lock solenoid (24), center cross-axle lock solenoid (25), and rear cross-axle lock solenoid (26).When necessary, the Chassis ECM will ENERGIZE one or more of the three XAD lock solenoids which sends oil flow to the respective XAD.The Inter-Axle Differential (IAD) lock works with the XAD lock to distribute power to the front and rear axles as needed. Along with the engagement of the IAD system, this action places the TCS in a mode that ensures that front to rear, and side to side, the wheels with the best traction receive the most power. This engagement increases the efficiency of the distribution of power and torque from the transmission.The cross-axle differential clutch may not lock completely as the cross-axle lock control solenoids are proportional valves. The valve locks the left and right wheels together proportionally to the extent of "lockup" the ATC system requires.The same operation occurs on the center and front axles when the ECM detects a difference in wheel speeds on those axles.The ATC system will partially engage the differential lock clutches on grades above 12%, whether there is a loss of traction or not. This partial engagement is done so the ATC system can react more quickly to a loss in traction on a grade. At grades above 12%, the XAD lock clutches will be partially engaged and remain at that level as the grade increases. At a grade of 12%, the IAD lock clutch will partially engage but will increase engagement as the grade increases.
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Monitor indicator dash Panel
(32) ATC Fault indicator lampWhen a fault in the ATC System occurs, the ATC fault indicator lamp is illuminated amber.ECM and