Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual - part 422

6MT-25

General Description

MANUAL TRANSMISSION AND DIFFERENTIAL

2. GENERAL TOOL

18675AA000

DIFFERENTIAL 
SIDE OIL SEAL 
INSTALLER

Used for installing the differential side retainer oil 
seal.

28399SA010

OIL SEAL PROTEC-
TOR

Used for protecting oil seal when installing front 
drive shaft.

18657AA020

OIL SEAL 
INSTALLER

Used for installing the oil seal.

18270KA020

SOCKET (E20)

Used for removing and installing the hypoid 
driven gear.

TOOL NAME

REMARKS

Circuit tester

Used for measuring resistance, voltage and current.

TORX

®

 bit T70

Used for removing and installing transmission gear oil drain 
plug.

Depth gauge

Used for measuring the transmission end play.

ILLUSTRATION

TOOL NUMBER

DESCRIPTION

REMARKS

ST18675AA000

ST28399SA010

ST18657AA020

ST18270KA020

6MT-26

Transmission Gear Oil

MANUAL TRANSMISSION AND DIFFERENTIAL

2. Transmission Gear Oil

A: INSPECTION

1) Lift up the vehicle.

2) Remove the transmission under cover.

3) Remove the filler plug, and then check the trans-

mission gear oil.

4) Check that the transmission gear oil level is up to

the bottom of the filler plug. If the transmission gear

oil level is low, refill up to the bottom of filler plug.

5) Using a new gasket, and tighten the filler plug.
Tightening torque:

50 N·m (5.1 kgf-m, 36.9 ft-lb)

B: REPLACEMENT

1) Lift up the vehicle.

2) Remove the transmission under cover.

3) Remove the filler plug.

4) Remove the two drain plugs (oil pan side, clutch

housing side), and then drain the transmission gear

oil completely.
CAUTION:

• Immediately after running the vehicle or after

idling for a long time, the transmission gear oil

will be hot. Be careful not to receive burns.

• Be careful not to spill the transmission gear

oil on exhaust pipe to prevent it from emitting

smoke or causing fires. If transmission gear oil

is spilled on the exhaust pipe, wipe it off com-

pletely.
NOTE:

• Tighten the drain plug of the transmission gear

oil after draining the transmission gear oil.

• Always use a new gasket.

• Use  TORX

®

  bit  T70  to  remove  and  install  the

drain plug on clutch housing side.
Tightening torque:

Oil pan side

50 N·m (5.1 kgf-m, 36.9 ft-lb)

Clutch housing side

70 N·m (7.1 kgf-m, 51.6 ft-lb)

5) Pour transmission gear oil to the bottom end of

filler plug.
NOTE:

Carefully refill transmission gear oil while checking

the  level.  Excessive  or  insufficient  oil  must  be

avoided.
Recommended gear oil

GL-5 (75W-90) or equivalent

Transmission gear oil capacity

4.1 L (4.3 US qt, 3.6 Imp qt)

6) Check the level of the transmission gear oil.

7) Using a new gasket, and tighten the filler plug.
Tightening torque:

50 N·m (5.1 kgf-m, 36.9 ft-lb)

(A) Filler plug

(A) Filler plug

MT-01706

(A)

MT-01706

(A)

(A) Drain plug (oil pan side)
(B) Drain plug (clutch housing side)

MT-01830

(A)

(B)

6MT-27

Oil Seal

MANUAL TRANSMISSION AND DIFFERENTIAL

3. Oil Seal

A: INSPECTION

Check that there is no oil leaking from the oil seal.

If there is any deformation, hardening, wear or oth-

er malfunctions of the oil seal, perform the follow-

ing:

• Replace the oil seal.

• Inspect the propeller shaft.

B: REPLACEMENT

1) Clean the transmission exterior.

2) Drain transmission gear oil completely. <Ref. to

6MT-26,  REPLACEMENT,  Transmission  Gear

Oil.>

3) Remove  the  rear  exhaust  pipe  and  muffler.

<Ref.  to  EX(STI)-13,  REMOVAL,  Rear  Exhaust

Pipe.> <Ref. to EX(STI)-15, REMOVAL, Muffler.>

4) Remove the heat shield cover.

5) Remove the propeller shaft. <Ref. to DS-11, RE-

MOVAL, Propeller Shaft.>

6) Using the ST, remove the oil seal.

ST 398527700

PULLER ASSY

7) Using the ST, install the oil seal.
NOTE:

• When grease is not applied to the oil seal lips,

apply the transmission gear oil to the oil seal lips.

• Use a new oil seal.

ST 498057300

INSTALLER

8) Install  the  propeller  shaft.  <Ref.  to  DS-12,  IN-

STALLATION, Propeller Shaft.>

9) Install the heat shield cover.

10) Install the rear exhaust pipe and muffler. <Ref.

to  EX(STI)-13,  INSTALLATION,  Rear  Exhaust

Pipe.> <Ref. to EX(STI)-15, INSTALLATION, Muf-

fler.>

11) Pour in transmission gear oil and check the oil

level.  <Ref.  to  6MT-26,  REPLACEMENT,  Trans-

mission Gear Oil.>

(A) Oil seal

MT-00451

(A)

ST

MT-00099

6MT-28

Differential Side Retainer Oil Seal

MANUAL TRANSMISSION AND DIFFERENTIAL

4. Differential Side Retainer Oil 

Seal

A: INSPECTION

Check that there is no oil leaking from the differen-

tial side retainer oil seal. If there is oil leakage, per-

form the following procedures.

• Replace the oil seal.

• Check the front drive shaft.

B: REPLACEMENT

1) Lift up the vehicle.

2) Remove  the  front  exhaust  pipe  and  center  ex-

haust pipe. <Ref. to EX(STI)-6, REMOVAL, Front

Exhaust Pipe.>

3) Drain transmission gear oil completely. <Ref. to

6MT-26,  REPLACEMENT,  Transmission  Gear

Oil.>

4) Separate the front drive shaft from the transmis-

sion.  <Ref.  to  DS-27,  REMOVAL,  Front  Drive

Shaft.>

5) Remove the differential side retainer oil seal by

using a flat tip screwdriver or similar tools.

6) Using the ST, install the differential side retainer

oil seal by lightly tapping with a hammer.

ST 18675AA000 DIFFERENTIAL SIDE OIL 

SEAL INSTALLER

7) Apply transmission gear oil to the oil seal lips.

8) Set the ST to the side retainer.

ST 28399SA010 OIL SEAL PROTECTOR

9) Install the front drive shaft into the transmission.
NOTE:

Replace the circlip of drive shaft with a new part.

10) Install the front drive shaft into transmission, re-

move the ST and insert the drive shaft securely.

ST 28399SA010 OIL SEAL PROTECTOR

11) Install the front exhaust pipe and the center ex-

haust  pipe.  <Ref.  to  EX(STI)-6,  INSTALLATION,

Front Exhaust Pipe.>

12) Pour transmission gear oil to the bottom end of

filler  plug.  <Ref.  to  6MT-26,  REPLACEMENT,

Transmission Gear Oil.>

13) Lower the vehicle.