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7.22
FINAL DRIVE
Operation
Engaging Front Gearcase: Active Descent Control (ADC) is
controlled by the ECU and will not enable until the following
conditions are met:
• Vehicle speed is below 15 Mph (24Kph)
• Throttle Position Sensor (TPS) is at idle position
• The AWD switch is switched to ‘AWD’
Once the conditions are met for engagement, ADC remains
engaged as long as the conditions are met.
With the AWD switch off, the vehicle drives only the rear
wheels (2 wheel drive). When the AWD switch is ‘ON’ the
magnetic coils are active, the AWD coil indexes the clutch
mechanism so that both front axles will engage when there is a
loss of rear wheel traction. In addition to the rear wheel engine
braking, the ADC coil provides front wheel engine braking at
speeds less than 15 Mph (24Kph) with the TPS at idle position.
ADC Engagement: When the AWD switch is activated, a 12
Vdc current is present at the input shaft coil (1). Operation is
controlled by the ECU grounding and ungrounding the coil. The
coil’s magnetic field attracts a splined armature plate (2) on the
pinion (input) shaft (4). The energized splined armature plate
attracts the unsplined eccentric cam (3), which begins to turn
with the input shaft. The eccentric cam drives a hydraulic
piston/pump assembly (5). The pressure created by the pump
assembly forces hydraulic fluid through passages to the piston
assemblies (6) located in each case half. Hydraulic pressure
forces the piston assemblies inward to compress the splined
clutch packs (7) forming a dynamic coupling to each front drive
axle, resulting in true all-wheel EBS operation upon
deceleration.
Disengagement: Current to the ADC coil is turned off by the
ECU anytime the following conditions are met:
• Throttle Position Sensor (TPS) moves off idle position
• The AWD switch is switched to ‘OFF’
• Vehicle speed is above 15 Mph (24Kph)
Hydraulic pressure stops and the pistons release, disengaging
the ADC function. The vehicle returns to rear wheel drive until
the next deceleration.
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