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110
FIAT - 850 PASSENGER CARS
Fig. 175 - Checking gear backlash.
1. Magnetic dial indicator. - 2. Second driven gear.
Slip sleeves should not be excessively worn
either on their interior face or at serrations mating
with gears; also, the synchro ring must show no
undue play in its seat on gear.
The synchro ring face which contacts the slip
sleeve and the toothed crown of the gear,
is
coated
with a layer of molibdenum which confers
it
a high
degree of wear resistance and a rather rough look.
The overall diameter of the ring of all synchronizer
units, in place in the gear and in a new condition,
is 2.6071" ± .0079··. (66.22 ±0.2 rom) (fig. 168).
After a certain number of gear shifts, during
which the synchromesh ring has set by riding
against the gear toothed crown and the slip sleeve,
the ring diameter will change to 2.6102·'
±
.0079'·
(66.3 ±O.2 rom), which turns out to be the best
suited for a perfect synchromesh.
Fig. 1TI • Drive pinion bearing in place in transmission case.
1. Ball bearing .• 2. Lock plate. - 3. Bearing screw.
If
the synchro ring must be replaced, check that
the overall diameter of the new ring, when seated
in
the gear, corresponds to specifications.
All gaskets and seals must be in top condition;
renew
if
there
is
the slightest doubt as to their
efficiency.
Shifter rail detent balls and safety rollers should
slide freely in their seats.
Bound balls or rollers
may cause irregular engagement or spontaneous
disengament of gears.
Shifter forks must not be distorted and rails
should slide snugly in their guide bores,
with
no
appreciable play.
14
11
1\
10
16
9
8
J
\
1
7
6
Check gear backlash: it should be .004" (0.10 rom)
with
new gears; wear limit is .008" (fig. 175).
Slip sleeves and hubs should show mirror-like
sliding faces.
Fig. 176 _ Cross sectional view of transmission side cover
assembly.
1. Cover. - 2. Gear selector lever spindle. - 3. Bushing. - 4. Cover
for shifter rail detent balls and springs. - 5. First and second shifter
rail safety roller. - 6. Detent ball spring.• 7. Shifter rail detent ball.-
8. First and second shifter rait. - 9. Third and fourth shifter rail.•
10. Third and fourth shifter rail safely roller. - 11. First and second
shifter fork. - 12. Third and fourth shifter fork. - 13. Reverse shifter
rail safely roller. - 14. Reverse shifter fork. - 15. Reverse shifter rail.-
16. Shilter rail safety roller seating plug.
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