Front Servo; Drive Range; Rear Servo - Jeep 1979 CJ-5 Technical & Service Manual

2C-4 AUTOMATIC TRANSMISSION
weights is transmitted to the regulator valve causing the
valve to send a pressure signal that increases with ve-
hicle speed.
Front Servo
The front servo applies the front band to provide
engine braking action in second gear in the 2 and 1
gearshift positions. The front servo also functions as an
accumulator in applying the direct clutch. In con-
junction with a series of check balls and controlling
orifices, the servo also assists in timing direct clutch
release.
To prevent front band application in Neutral, Drive
and Reverse, oil is directed from the manual valve to the
release side of the servo piston.
In Drive range, servo release oil from the manual
valve is used to charge the servo in preparation for
direct clutch application.
Direct clutch oil is applied to the front servo accu-
mulator piston where spring force, plus direct clutch
pressure, moves the piston upward against the force of
servo release oil. This decreases clutch apply pressure
for smoother engagement.
The release of the direct clutch and exhausting of the
front servo accumulator is slowed by three check balls
and three orifices for smoother return of drive load to
the intermediate roller clutch.
Drive Range—First Gear
Front servo oil from the manual valve charges the
accumulator by moving the servo and accumulator pis-
tons against the accumulator spring. This prepares the
accumulator for controlled direct clutch apply on 2-3
upshifts. Charging the accumulator in Drive range-first
gear also provides controlled 1-3 lift-foot upshifts as the
accumulator is prepared for direct clutch apply in first
gear.
Servo oil and servo release spring tension prevent
band application in Drive range-second gear when inter-
mediate clutch apply oil is directed between the servo
and accumulator pistons.
Drive Range—Second Gear
Servo oil charging the accumulator is present in first
and second gears and moves the servo and accumulator
pistons against the accumulator spring.
In second gear, intermediate clutch oil is directed be-
tween the servo and accumulator pistons but does not
separate the pistons. At this point, the force of servo oil
holding the piston down is equal to the force of inter-
mediate clutch oil attempting to move the piston
upward.
Drive Range—Third Gear
An increase in direct clutch pressure, plus accumula-
tor spring force overcomes servo pressure and moves the
accumulator piston to the accumulator piston pin stop.
This moves the servo piston at the same amount of
travel allowing the piston to just contact the band-apply
washer on the servo pin, but not move the pin and apply
the band.
Movement of the accumulator piston absorbs some
direct clutch oil and permits reduced pressure direct
clutch application for smoother 2-3 upshifts.
Drive Range—3-2 Downshift
Direct clutch release is softened by the front servo,
three orifices, and three check balls for a smoother
transfer of drive load to the intermediate roller clutch.
The controlled release pressure permits an increase in
engine rpm during detent downshifts to prepare for the
lower gear ratio of second gear, resulting in a smoother
shift and acceleration.
Servo oil and intermediate clutch oil seat two check
balls which direct oil through two orifices, slowing
movement of the servo and accumulator pistons. Direct
clutch oil that is exhausted from the accumulator and
direct clutch seats a third check ball. This channels oil
being exhausted from the direct clutch through an ori-
fice which controls direct clutch pressure during clutch
release.
Drive-2 Range—First Gear
Intermediate clutch oil from the 1-2 shift valve seats
the check ball and is directed through an orifice to apply
the front band. Band apply pressure is reduced by accu-
mulator piston movement which is prompted by inter-
mediate clutch oil. It is further resisted by accumulator
spring tension and by oil exhausted from the direct
clutch.
Rear Servo
The rear servo applies the rear band for overrun en-
gine braking in Drive-1 range. It applies the band in
Reverse to hold the reaction carrier to provide the re-
verse gear ratio.
On the 1-2 shift in Drive and Drive-2 ranges, the rear
servo operates as an accumulator for the intermediate
clutch to provide smoother shifts.
Rear Servo—Drive-1 Range
In Drive-1 and Drive-2 ranges, 1-2 accumulator oil is
directed to the rear servo accumulator piston in prepara-
tion for the 1-2 shift.
Rear Servo—Drive-2 Range
Intermediate clutch apply oil is directed to the rear
servo accumulator piston moving the piston against 1-2
accumulator oil and the accumulator spring. This action
absorbs some intermediate clutch apply oil permitting