Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 413

5MT-73

Front Differential Assembly

MANUAL TRANSMISSION AND DIFFERENTIAL

E: INSPECTION

Repair or replace the differential gear in the follow-

ing cases:

• When the hypoid drive gear and drive pinion

shaft tooth surfaces are damaged, excessively

worn, or seized.

• When the roller bearing on the drive pinion shaft

has a worn or damaged roller path.

• When there is damage, wear or seizure of the dif-

ferential bevel pinion, differential bevel gear, ad-

justing washer, pinion shaft or straight pin.

• When the differential case sliding surfaces are

worn or damaged.

1. BEVEL PINION GEAR BACKLASH

Measure the backlash between the differential bev-

el gear and differential bevel pinion. If backlash is

out of specifications, install a suitable adjusting

washer to adjust. <Ref. to 5MT-74, ADJUSTMENT,

Front Differential Assembly.>
NOTE:

Be sure the pinion gear teeth contacts adjacent

gear teeth during measurement.

ST1 498247001

MAGNET BASE

ST2 498247100

DIAL GAUGE

Standard backlash

0.13 — 0.18 mm (0.0051 — 0.0071 in)

2. HYPOID GEAR BACKLASH

1) Set the ST1, ST2 and ST3. Insert the needle

through transmission oil drain plug hole so that the

needle comes in contact with the tooth surface on

the right corner, and check the backlash.

ST1 498247001

MAGNET BASE

ST2 498247100

DIAL GAUGE

ST3 498255400

PLATE

2) Install SUBARU genuine axle shafts to both

sides, rotate in the inversion direction so that the

gauge contacts the tooth surface, and read the dial

gauge

Part No. 38415AA100 Axle shaft
Backlash

0.13 — 0.18 mm (0.0051 — 0.0071 in)

NOTE:

If the backlash is outside the specified range, ad-

just it by turning the side retainer in the right side

case.

(A) Drive pinion shaft
(B) Hypoid driven gear

(C) Pinion shaft
(D) Straight pin

(E) Adjusting washer

(F) Differential bevel gear

(G) Differential bevel pinion

(H) Roller bearing

(I) Differential case

(I)

(H)

(D)

(C)

(B)

(E)

(F)

(G)

(F)

(E)

(A)

(H)

(G)

MT-01074

MT-00285

ST1

ST2

MT-00293

ST1

ST2

ST3

5MT-74

Front Differential Assembly

MANUAL TRANSMISSION AND DIFFERENTIAL

3. TOOTH CONTACT OF HYPOID GEAR

Check tooth contact of hypoid gear as follows: Ap-

ply a thin uniform coat of red lead on both teeth sur-

faces on 3 or 4 teeth of the hypoid gear. Move the

hypoid gear back and forth by turning the transmis-

sion main shaft until a definite contact pattern is de-

veloped on the hypoid gear, and judge whether

face contact is correct. When the contact pattern is

not correct, adjust. <Ref. to 5MT-74, ADJUST-

MENT, Front Differential Assembly.>

• Tooth contact is correct.

F: ADJUSTMENT

1. BEVEL PINION GEAR BACKLASH

1) Disassemble the front differential assembly.

<Ref. to 5MT-70, DISASSEMBLY, Front Differen-

tial Assembly.>

2) Select a suitable adjusting washer for the differ-

ential bevel gear from the table and install.

3) Adjust until the standard value is obtained.
Backlash:

Standard

0.13 — 0.18 mm (0.0051 — 0.0071 in)

2. HYPOID GEAR BACKLASH

Adjust the backlash by turning the side retainer in

the RH side case.

ST 18630AA010 WRENCH COMPL RETAIN-

ER

NOTE:

Each time the side retainer rotates by one notch

(A), the backlash changes by 0.05 mm (0.020 in).

(A) Toe
(B) Coast side

(C) Heel
(D) Drive side

Adjusting washer

Part No.

Thickness mm (in)

803038021

0.925 — 0.950

(0.0364 — 0.0374)

803038022

0.975 — 1.000

(0.0384 — 0.0394)

803038023

1.025 — 1.050

(0.0404 — 0.0413)

MT-01402

(B)

(D)

(C)

(A)

MT-00176

ST

MT-02603

(A)

5MT-75

Front Differential Assembly

MANUAL TRANSMISSION AND DIFFERENTIAL

3. TOOTH CONTACT OF HYPOID GEAR

1) Adjust until correct teeth contact is obtained.

2) Check tooth contact, and perform the adjust-

ment as follows.

• Correct tooth contact

Check item: Tooth contact surface is slightly

shifted toward the toe side under a no-load con-

dition. (When driving, it moves towards the heel

side.)

• Face contact

Check item: Backlash is too large.

Contact pattern

Corrective action: Tighten the side retainer to move

the driven gear closer to the drive pinion shaft.

• Flank contact

Check item: Backlash is too small.

Contact pattern

Corrective action: Loosen the side retainer to move

the driven gear away from the drive pinion shaft.

• Toe contact (inside contact)

Check item: Teeth contact area is too small.

Contact pattern

Corrective action: Increase the thickness of drive

pinion shim and tighten the side retainer to move

the driven gear closer to the drive pinion shaft ac-

cording to the procedure for bringing drive pinion

shaft away from driven gear.

(A) Toe side
(B) Heel side

(A)

(B)

MT-01401

AT-00208

MT-01799

AT-00209

MT-01800

AT-00210

AT-00213

5MT-76

Front Differential Assembly

MANUAL TRANSMISSION AND DIFFERENTIAL

• Heel contact (outside end contact)

Check item: Teeth contact area is too small.

Contact pattern

Corrective action: Reduce the thickness of drive

pinion shim and loosen the side retainer to move

the driven gear away from the drive pinion accord-

ing to the procedure for moving drive pinion shaft

closer to the driven gear.

AT-00211

AT-00212