M20 GEARBOX
FIAT PUNTO TRAINING OUTLINE
Fiat Auto S.p.A.
After Sales Training
The synchromesh features a triple-cone design on the 1
st
and 2
nd
gears (i.e. the gears most
frequently used and subjected to stress) and a double-cone design on the 3
rd
and 4
th
gears, to
ensure significantly lower engaging effort compared with a traditional, single-cone
synchromesh of equal dimensions.
The new internal gear control system, which provides for 4 selection levels, with central
bearing gear positioner, gives the advantage of low hysteresis and, therefore, smaller gear
selection loads.
The wheels and kinematic mechanisms inside the gearbox are lubricated dynamically through
channelled oil flow paths through holes on the cases and shafts. This ensures better torque
transmission performance and higher efficiency in terms of wear and manoeuvrability even at
low temperatures, thanks to the use of multigrade oil.
5.2 Component
5.2.1 Synchromesh
The M32-6 gearbox features the upgraded synchromesh unit previously fitted to the F40
manual gearbox. The synchronization springs and pins used so far have been replaced by
push dowels. Accurate synchromeshes are used with the single gears, too. Two- or three-
cone synchromeshes are used. Below are some illustrations that show the synchromeshes
used with every single gear.
1
st
/2
nd
gears
The three-cone synchromesh is used with the 1
st
and 2
nd
gears.
1. Inner synchromesh ring
2. Intermediate ring
3. Outer synchromesh ring
4. Engaging sleeve
5. Synchromesh hub
gb Fiat Grande Punto OK
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6. Push dowels