Subaru IMPREZA GD 2007 Series Manual page 3034

asieps_tobira_IM_US.book 129 ページ ２０１２年１月１７日 火曜日 午後３時４８分
2. DIFFERENTIAL
Symptom
1. Broken differential (case, gear, bear-
ing, etc.)
NOTE:
Noise will occur, and eventually the differ-
ential will not be able to operate due to
broken pieces obstructing the gear revo-
lution.
2. Differential and hypoid gear noise
Troubles of the differential and hypoid
gear always appear as noise problems.
Therefore noise is the first indication of
trouble. However, noise from the engine,
muffler, tire, exhaust gas, bearing, body,
etc. are easily mistaken for noise from the
differential. 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 while 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 during coasting: Damaged
gears due to misadjusted bearings and
incorrect shim adjustment.
• Noise from bearings during driving or
during coasting: Bearing cracked, dam-
aged.
• Noise occurring mainly during a turn:
Noise from the differential side gear, dif-
ferential pinion, differential pinion shaft
General Diagnostic Table
MANUAL TRANSMISSION AND DIFFERENTIAL
Possible cause
(a) Insufficient or improper oil
(b) Use of vehicle under severe condi-
tions such as excessive load and
improper use of the clutch
(c) Improper adjustment of taper roller
bearing
(d) Improper adjustment of the drive pin-
ion and the hypoid driven gear
(e) Loose hypoid driven gear clamping
bolts
(a) Insufficient oil
(b) Improper adjustment of hypoid driven
gear and drive pinion
(c) Worn teeth of hypoid driven gear and
drive pinion
(d) Loose roller bearing
(e) Distorted hypoid driven gear or differ-
ential case
(f) LSD broken, damaged, etc.
6MT-129
Corrective action
Replace.
Replace.
Adjust.
Adjust.
Tighten.
Lubricate.
Check the tooth contact.
Replace as a set.
Readjust the bearing preload.
Readjust the backlash of the hypoid
driven gear to drive pinion, and check the
tooth contact.
Replace.
Replace.