Subaru Impreza 2003, Service Manual

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5MT-120
MANUAL TRANSMISSION AND DIFFERENTIAL
GENERAL DIAGNOSTIC
25.General Diagnostic
A: INSPECTION
1. MANUAL TRANSMISSION
Symptom Possible cause Remedy
1. Gears are difficult to intermesh.
NOTE:
The cause for difficulty in shifting gears
can be classified into two kinds: one is
malfunction of the gear shift system and
the other is malfunction of the transmis-
sion. However, if the operation is heavy
and engagement of the gears is difficult,
defective clutch disengagement may also
be responsible. Check whether the clutch
is correctly functioning, before checking
the gear shift system and transmission. (a) Worn, damaged or burred chamfer of
internal spline of sleeve and reverse
driven gear Replace.
(b) Worn, damaged or burred chamfer of
spline of gears Replace.
(c) Worn or scratched bushings Replace.
(d) Incorrect contact between synchro-
nizer ring and gear cone or wear Correct or replace.
2. Gear slips out.
• Gear slips out when coasting on rough
road.
• Gear slips out during acceleration. (a) Defective pitching stopper adjustment Adjust.
(b) Loose engine mounting bolts Tighten or replace.
(c) Worn fork shifter, broken shifter fork
rail spring Replace.
(d) Worn or damaged ball bearing Replace.
(e) Excessive clearance between splines
of synchronizer hub and synchronizer
sleeve Replace.
(f) Worn tooth step of synchronizer hub
(responsible for slip-out of 3rd gear) Replace.
(g) Worn 1st driven gear and driven shaft Replace.
(h) Worn 2nd driven gear and bushing Replace.
(i) Worn 3rd drive gear and needle bear-
ing Replace.
(j) Worn 4th drive gear and needle bear-
ing Replace.
(k) Worn reverse idler gear and bushing Replace.
3. Unusual noise comes from transmis-
sion.
NOTE:
If an unusual noise is heard when the ve-
hicle is parked with its engine idling and if
the noise ceases when the clutch is disen-
gaged, it may be considered that the
noise comes from the transmission. (a) Insufficient or improper lubrication Lubricate or replace with specified oil.
(b) Worn or damaged gears and bearings
NOTE:
If the trouble is only wear of the tooth sur-
faces, merely a high roaring noise will oc-
cur at high speeds, but if any part is
broken, rhythmical knocking sound will be
heard even at low speeds. Replace.