Chevrolet Light Duty Truck 1973, Service Manual

Page: 696 / 979

7 A - 5 4 A U T O M A T IC T R A N S M IS S IO N
Fig. 15T—Front Servo
Front Servo (Fig. 15T)
The front servo applies the front overrun band to
provide engine braking in 2nd gear in L2 Range. It is
also used as an accumulator for the application of the
direct dutch and in conjunction with a series of check
balls and controlling orifices is a part of the timing for
the release of the direct clutch.
To prevent the application of the front overrun band in
Neutral, Drive and Reverse ranges, oil is directed from
the manual valve to the release side of the servo piston.
In Drive range the servo release oil from the manual
valve also acts to charge the servo in preparation for the
application of the direct clutch.
Direct clutch oil is directed to the front servo
accumulator piston where spring force plus direct clutch
pressure stroke the piston up against the force of servo
TO INT CL.
Fig. 16T—Rear Servo
release oil. This lowers the clutch apply pressure during
the shift for a smooth engagement.
The release of the direct clutch and the exhausting of the
front servo accumulator is slowed down by three check
balls and three orifices which permits a soft return of the
drive load to the intermediate roller clutch and also
allows engine RPM to increase during a detent 3-2
downshift in preparation for the lower gear ratio, which
results in a smooth shift and better acceleration.
Rear Servo (Fig. 16T)
The rear servo applies the rear band for overrun engine
braking in LI range 1st gear. It applies the band in
Reverse to hold the reaction carrier to provide the
reverse gear ratio.
LIGHT DUTY TRUCK SERVICE MANUAL