Service Manual

8.13
FINAL DRIVE
8
ADC Operation
Engaging the 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 (24 kph)
• Throttle Position Sensor (TPS) is at idle position
• The AWD switch is switched to the “ADC” position
Once the conditions are met for engagement, ADC remains
engaged as long as the conditions are met.
With the AWD switch set to “2x4”, the vehicle drives only the
rear wheels (2 wheel drive). When the AWD switch is set to
“4x4”, the vehicle drives all four wheels (4 wheel drive). When
the AWD switch is set to “4x4/ADC”, the vehicle drives all four
wheels and, in addition to the rear wheel engine braking, the
ADC coil provides front wheel engine braking at speeds less
than 15 mph (24 kph) with the TPS at idle position.
ADC Engagement: When the AWD switch is set to “4x4/
ADC”, 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 “4x4” or “2x4”
• Vehicle speed is above 15 mph (24 kph)
Hydraulic pressure stops and the pistons release, disengaging
the ADC function.