Page 1665 of 2399
PLANETARY GEARTRAIN
DISASSEMBLY
(1) Remove snap ring and #4 thrust washer (Fig.
185)
(2) Remove annulus gear support front snap ring
(Fig. 186).(3) Remove annulus gear support and snap ring
(Fig. 187).
(4) Remove remaining snap ring (Fig. 188).
Fig. 185 Front Planetary Gear Snap Ring and No. 4
Thrust Washer
1 - SNAP RING
2 - #4 THRUST WASHER
3 - SNAP RING
4 - FRONT PLANETARY GEAR ASSEMBLY
Fig. 186 Annulus Gear Support Front Snap Ring
1 - ANNULUS GEAR SUPPORT
2 - FRONT SNAP RING
3 - SCREWDRIVER
4 - FRONT PLANETARY ANNULUS GEAR
Fig. 187 Front Annulus Gear Support and Snap Ring
1 - FRONT ANNULUS GEAR
2 - FRONT SNAP RING
3 - FRONT ANNULUS GEAR SUPPORT
4 - REAR SNAP RING
Fig. 188 Front Annulus Gear Support Snap Ring
1 - FRONT ANNULUS GEAR
2 - REAR SNAP RING
21 - 108 31TH AUTOMATIC TRANSAXLERS
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Page 1666 of 2399
(5) Remove and inspect front planetary carrier
assembly (Fig. 189).
ASSEMBLY
(1) Install front planetary gear assembly to annu-
lus gear (Fig. 190).(2) Install first support snap ring (Fig. 191).
(3) Install annulus gear support and snap ring
(Fig. 192).
Fig. 189 Front Planetary Gear
1 - FRONT PLANETARY GEAR ASSEMBLY
Fig. 190 Front Planetary Gear
1 - FRONT PLANETARY GEAR ASSEMBLY
Fig. 191 Front Annulus Gear Support Snap Ring
1 - FRONT ANNULUS GEAR
2 - REAR SNAP RING
Fig. 192 Front Annulus Gear Support and Snap Ring
1 - FRONT ANNULUS GEAR
2 - FRONT SNAP RING
3 - FRONT ANNULUS GEAR SUPPORT
4 - REAR SNAP RING
RS31TH AUTOMATIC TRANSAXLE21 - 109
PLANETARY GEARTRAIN (Continued)
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Page 1667 of 2399

(4) Install a NEW front planetary gear snap ring
and #4 thrust washer (Fig. 193).
SEAL - OIL PUMP
REMOVAL
The pump oil seal can be replaced without remov-
ing the pump and reaction shaft support assembly
from the transaxle case.
(1) Screw seal remover Tool C-3981-B into seal
(Fig. 194), then tighten screw portion of tool to with-
draw the seal.
INSTALLATION
The pump oil seal can be replaced without remov-
ing the pump and reaction shaft support assembly
from the transaxle case.
(1) To install a new seal, place seal in opening of
the pump housing (lip side facing inward). Using Tool
C-4193 and Handle Tool C-4171, drive new seal into
housing until tool bottoms (Fig. 195).
Fig. 193 Front Planetary Gear Snap Ring and No. 4
Thrust Washer
1 - SNAP RING
2 - #4 THRUST WASHER
3 - SNAP RING
4 - FRONT PLANETARY GEAR ASSEMBLY
Fig. 194 Remove Pump Oil Seal
1 - PUMP OIL SEAL
2 - OIL SEAL REMOVER TOOL C-3981-B
3 - OIL PUMP
Fig. 195 Install Pump Oil
1 - OIL PUMP
2 - OIL SEAL INSTALLER TOOL C-4193
3 - SPECIAL TOOL HANDLE C-4171
21 - 110 31TH AUTOMATIC TRANSAXLERS
PLANETARY GEARTRAIN (Continued)
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Page 1668 of 2399

SERVO - KICKDOWN
DESCRIPTION
The kickdown servo (Fig. 196) consists of a two-
land piston with an inner piston, a piston rod and
guide, and a return spring. The dual-land piston uses
seal rings on its outer diameters and an O-ring for
the inner piston.
OPERATION
The application of the piston is accomplished by
applying pressure between the two lands of the pis-
ton. The pressure acts against the larger lower land
to push the piston downward, allowing the piston rod
to extend though its guide against the apply lever.
Release of the servo at the 2-3 upshift is accom-
plished by a combination of spring and line pressure,
acting on the bottom of the larger land of the piston.
The small piston is used to cushion the application of
the band by bleeding oil through a small orifice in
the larger piston. The release timing of the kickdown
servo is very important to obtain a smooth but firm
shift. The release has to be very quick, just as the
front clutch application is taking place. Otherwise,
engine runaway or a shift hesitation will occur. To
accomplish this, the band retains its holding capacity
until the front clutch is applied, giving a small
amount of overlap between them.
DISASSEMBLY
(1) Remove kickdown servo snap ring (Fig. 197).
(2) Remove kickdown servo rod guide and snap
ring (Fig. 198).
Fig. 196 Front Servo
1 - VENT
2 -PISTON ROD
3 - PISTON
4 - SPRING
5 - RELEASE PRESSURE
6 - APPLY PRESSURE
Fig. 197 Kickdown Servo Snap Ring
1 - SNAP RING
2 - SNAP RING PLIERS
3 - ACCUMULATOR PLATE
4 - KICKDOWN LEVER
5 - KICKDOWN PISTON ROD GUIDE
Fig. 198 Kickdown Servo Rod Guide and Snap Ring
1 - SNAP RING
2 - ACCUMULATOR PLATE
3 - RETURN SPRING
4 - O-RING
5 - PISTON ROD GUIDE
RS31TH AUTOMATIC TRANSAXLE21 - 111
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(3) Remove kickdown piston return spring and pis-
ton (Fig. 199).
(4) Disassemble piston assembly as shown in (Fig.
200).CLEANING
Clean the servo piston components (Fig. 201) with
solvent and dry them with compressed air. Wipe the
band clean with lint free shop towels.
Replace the front band if distorted, lining is
burned, flaking off, or worn to the point where the
grooves in the lining material are no longer visible.
Replace any servo component if doubt exists about
condition. Do not reuse suspect parts.
Fig. 199 Kickdown Piston Return Spring and Piston
1 - RETURN SPRING
2 - KICKDOWN LEVER
3 - PISTON ROD
4 - KICKDOWN SERVO PISTON
Fig. 200 Controlled Load Kickdown Servo
1 - KICKDOWN PISTON
2 - O-RING
3 - SNAP RING
4 - PISTON ROD GUIDE
5 - SNAP RING
6 - O-RING
7 - PISTON RETURN SPRING
8 - PISTON ROD
9 - SEAL RINGS
Fig. 201 Front Servo Piston
1 - PISTON RINGS
2 - O-RING
3 - SNAP-RING
4 - SEAL RING
5 - PISTON ROD GUIDE
6 - SNAP-RING
7 - SERVO SPRING
8 - PISTON ROD
9 - SERVO PISTON
21 - 112 31TH AUTOMATIC TRANSAXLERS
SERVO - KICKDOWN (Continued)
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INSPECTION
Inspect the servo components (Fig. 202). Replace
the springs if collapsed, distorted or broken. Replace
the guide, rod and piston if cracked, bent, or worn.
Discard the servo snap-ring if distorted or warped.
Check the servo piston bore for wear. If the bore is
severely scored, or damaged, it will be necessary to
replace the case.
ASSEMBLY
(1) Lubricate new O-ring and seal rings with
petroleum jelly and install them on piston, guide and
rod.
(2) Install rod in piston. Install spring and washer
on rod. Compress spring and install snap-ring (Fig.
203).
(3) Install piston and return spring (Fig. 199).
(4) Install rod guide and snap ring (Fig. 198) (Fig.
197).
SERVO - LOW/REVERSE
DESCRIPTION
The rear (low/reverse) servo consists of a single
stage or diameter piston and a spring loaded plug.
The spring is used to cushion the application of the
rear (low/reverse) band.
OPERATION
While in the de-energized state (no pressure
applied), the piston is held up in its bore by the pis-
ton spring. The plug is held down in its bore, in the
piston, by the plug spring. When pressure is applied
to the top of the piston, the plug is forced down in its
bore, taking up any clearance. As the piston moves, it
causes the plug spring to compress, and the piston
moves down over the plug. The piston continues to
move down until it hits the shoulder of the plug and
fully applies the band. The period of time from the
initial application, until the piston is against the
shoulder of the plug, represents a reduced shocking
of the band that cushions the shift.
Fig. 202 Front Servo Piston
1 - PISTON RINGS
2 - O-RING
3 - SNAP-RING
4 - SEAL RING
5 - PISTON ROD GUIDE
6 - SNAP-RING
7 - SERVO SPRING
8 - PISTON ROD
9 - SERVO PISTON
Fig. 203 Front Servo Piston
1 - PISTON RINGS
2 - O-RING
3 - SNAP-RING
4 - SEAL RING
5 - PISTON ROD GUIDE
6 - SNAP-RING
7 - SERVO SPRING
8 - PISTON ROD
9 - SERVO PISTON
RS31TH AUTOMATIC TRANSAXLE21 - 113
SERVO - KICKDOWN (Continued)
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Page 1671 of 2399
DISASSEMBLY
(1) Back off low/reverse band adjustment and posi-
tion lever out of the way (Fig. 204).
(2) Remove low/reverse servo snap ring (Fig. 205).
(3) Remove retainer, spring and servo (Fig. 206).
CLEANING
Remove and discard the servo piston seal ring (Fig.
207). Then clean the servo components with solvent
and dry with compressed air. Replace either spring if
collapsed, distorted or broken. Replace the plug and
piston if cracked, bent, or worn. Discard the servo
snap-rings and use new ones at assembly.
Fig. 204 Low/Reverse Lever
1 - LOW-REVERSE LEVER
Fig. 205 Low/Reverse Servo Snap Ring
1 - SNAP-RING PLIERS
Fig. 206 Remove Retainer, Spring and Servo
1 - SERVO PISTON
2 - SPRING AND RETAINER
Fig. 207 Rear Servo Components
1 - SNAP-RING
2 - PISTON SEAL
3 - PISTON PLUG
4 - SPRING RETAINER
5 - SNAP-RING
6 - PISTON SPRING
7 - CUSHION SPRING
8 - PISTON
21 - 114 31TH AUTOMATIC TRANSAXLERS
SERVO - LOW/REVERSE (Continued)
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Page 1672 of 2399

ASSEMBLY
(1) Install low/reverse servo assembly (Fig. 208).
(2) Install low/reverse servo snap ring (Fig. 205).
SHIFT INTERLOCK SOLENOID
DESCRIPTION
The Brake/Transmission Shift Interlock system
consists of an electro-magnetic solenoid mounted to
the steering column (Fig. 209). The solenoid's plunger
consists of an integrated hook, which operates the
shift lever pawl (part of shift lever assembly), and a
plunger return spring (Fig. 210). The solenoid also
has an integrated bracket, which facilitates fastening
to the steering column.
OPERATION
The Brake/Transmission Shift Interlock (BTSI)
Solenoid prevents the transmission shift lever from
being moved out of PARK (P) unless the brake pedal
is applied. The BTSI solenoid is hardwired to and
controlled by the Intelligent Power Module (IPM).
Battery voltage is applied to one side of the solenoid
with the ignition key is in either the OFF, ON/RUN,
or START positions (Fig. 211). The ground side of the
solenoid is controlled by a driver within the IPM. It
relies on voltage supplied from the stop lamp switch
to the stop lamp sense circuit within the IPM to tell
when the brake pedal is depressed. When the brake
pedal is depressed, the ground circuit opens, de-ener-
gizing the solenoid. When the brake pedal is
released, the ground circuit is closed, energizing the
solenoid.
Fig. 208 Low/Reverse Servo Assembly
1 - SERVO PISTON
2 - SPRINGFig. 209 Brake/Transmission Shift Interlock (BTSI)
Solenoid Location
1 - BTSI SOLENOID
Fig. 210 Solenoid Plunger and Return Spring
1 - PLUNGER
2 - RETURN SPRING
3 - BTSI SOLENOID
RS31TH AUTOMATIC TRANSAXLE21 - 115
SERVO - LOW/REVERSE (Continued)
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