Chevrolet Light Duty Truck 1973, Service Manual

Page: 713 / 979

A U T O M A T IC T R A N S M I S S I O N 7A-71
REVERSE RANGE-REVERSE GEAR
Power Flow
Forward Clutch - Off
Low Roller Clutch - Ineffective
Direct Clutch - On
Front Band - Off
Rear Band - On
Intermediate Clutch - Off
Intermediate Roller Clutch - Ineffective
Detent Solenoid - De-energized
In reverse gear, the direct clutch is applied to transmit
turbine torque from the forward clutch drum to the sun
gear shaft and sun gear. The rear band is also applied,
preventing the reaction carrier from turning clockwise.
Clockwise torque to the sun gear causes the front pinions
and front internal gear to turn counterclockwise in
reduction. The front internal gear is connected directly
to the output shaft, thus providing the reverse output
gear ratio of approximately 2.00:1. The reverse torque
multiplication at stall (converter and gear ratios) is
approximately 4.00:1.
Oil Flow
When the selector lever is moved to the Reverse position,
the manual valve is repositioned to allow line pressure to
enter the reverse circuit. Reverse oil then flows to the:
1. Direct Clutch
2. 2-3 Shift Valve
3. Rear Servo Piston
4. Pressure Boost Valve
Basic Control
Reverse oil from the manual valve flows to the large area
of the direct clutch piston and to the 2-3 shift valve.
From the 2-3 shift valve, it enters the direct clutch
passage and is directed to the small area of the direct
clutch piston to apply the direct clutch.
Reverse oil flows to the rear servo and acts on the servo
piston to apply the rear band. Reverse oil also acts on
the pressure boost valve to boost line pressure.
Summary
The direct clutch and the rear band are applied. The
transmission is in Reverse.
LIGHT DUTY TRUCK SERVICE MANUAL