Subaru Legacy (2005 year). Manual - part 663
5MT-99
MANUAL TRANSMISSION AND DIFFERENTIAL
General Diagnostic Table
2. DIFFERENTIAL
Symptom
Possible cause
Corrective action
1. Broken differential (case, gear, bear-
ing, etc.)
NOTE:
Noise will be developed and finally it will
become impossible to continue to run due
to broken pieces obstructing the gear rev-
olution.
(a) Insufficient or improper oil
Disassemble differential and replace bro-
ken components. 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
Adjustment.
(d) Improper adjustment of drive pinion
and hypoid driven gear
Adjustment.
(e) Excessive backlash due to worn dif-
ferential side gear, washer or differential
pinion under severe operating conditions
of the vehicle.
Add recommended oil to the specified
level. Do not use vehicle under severe
operating conditions.
(f) Loose hypoid driven gear tightening
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
trouble. However noises from the engine,
muffler, tire, exhaust gas, bearing, 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 fol-
lowing 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 bear-
ings and incorrect shim adjustment.
• Bearing noise when driving or coast-
ing:
Cracked, broken or rusty bearings
• Noise mainly when turning:
Noise occurs form differential side gear,
differential pinion or 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.