Subaru Impreza 2003, Service Manual

Page: 2061 / 3610

6MT-131
MANUAL TRANSMISSION AND DIFFERENTIAL
GENERAL DIAGNOSTIC TABLE
2. DIFFERENTIAL
Symptom Possible cause Remedy
1. Broken differential (case, gear, bear-
ing, etc.)
NOTE:
Abnormal noise will develop and finally it
will become impossible to continue to run
due to broken pieces obstructing the gear
revolution. (a) Insufficient or improper oil Disassemble differential and replace bro-
ken components and at the same time
check other components for any trouble,
and replace if necessary.
(b) Use of vehicle under severe condi-
tions such as excessive load and
improper use of clutch Readjust bearing preload and backlash
and face contact of gears.
(c) Improper adjustment of taper roller
bearing Adjust.
(d) Improper adjustment of drive pinion
and hypoid driven gear Adjust.
(e) Excessive backlash due to worn dif-
ferential side gear, washer or differential
pinion vehicle under severe operating
conditions. Add recommended oil to specified level.
Do not use vehicle under severe operat-
ing conditions.
(f) Loose hypoid driven gear clamping
bolts Tighten.
2. Differential and hypoid gear noises
Troubles of the differential and hypoid
gear always appear as noise problems.
Therefore noise is the first indication of
the trouble. However noises from the
engine, muffler, tire, exhaust gas, bear-
ing, body, etc. are easily mistaken for the
differential noise. Pay special attention to
the hypoid gear noise because it is easily
confused with other gear noises. There
are the following four kinds of noises.
• Gear noise when driving: If noise
increases as the vehicle speed increases
it may be due to insufficient gear oil,
incorrect gear engagement, damaged
gears, etc.
• Gear noise when coasting: Damaged
gears due to maladjusted bearings and
incorrect shim adjustment
• Bearing noise when driving or when
coasting: Cracked, broken or damaged
bearings
• Noise which mainly occurs when turn-
ing: Unusual noise from the differential
side gear, differential pinion, differential
pinion shaft, etc. (a) Insufficient oil Lubricate.
(b) Improper adjustment of hypoid driven
gear and drive pinion Check tooth contact.
(c) Worn teeth of hypoid driven gear and
drive pinion Replace as a set.
Readjust bearing preload.
(d) Loose roller bearing Readjust hypoid driven gear to drive pin-
ion backlash and check tooth contact.
(e) Distorted hypoid driven gear or differ-
ential case Replace.
(f) Worn washer and differential pinion
shaft Replace.