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DRIVETRAIN C549
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CONSTRUCTION SPECIFICATIONS
The C549 gearbox installed on the vehicle has
features aimed at improving maneuverability. Its
main features are:
Excellent maneuverability of the gear control
Quiet operation.
The configuration is transverse with 2 shafts
and a differential.
The design is being made to improve the
gearbox casing and the clutch casing in terms
of strength and noise absorption.
MAIN SHAFT
The main shaft consists of:
1st, 2nd speed and Reverse gears directly on
the shaft;
3rd, 4th and 5th speed gears fitted on the
shaft. The main shaft is supported by two ball
bearings.
LAYSHAFT
The lay shaft consists of:
1st, 2nd, 3rd, 4th and 5th speed gears fitted
on the shaft.
The lay shaft is mounted on:
a front roller bearing
a rear ball bearing.
GEARS
The gears are the following type:
helical toothed for the forward gears
Straight toothed for Reverse gear.
The teeth for all the gears are HCR (High Contact
Ratio). The 2nd and 5th speed and final drive
gears are super finished after the thermal
treatment to guarantee absolute precision for the
teeth and quiet Operation.
The kinematic components inside the gearbox
casing are lubricated dynamically, by means of
the oil flowing along channels and through ports in
the casings, the 3rd/4th speed rod and the main
shaft; this allows:
improved torque transmission and greater
efficiency against the effects of wear
Maneuverability even at low temperatures
thanks to the use of synthetic multi-grade oil.
SYNCHRONIZERS
The synchromesh for all the forward gears (there
is no synchromesh for reverse which is always
meshed on the main shaft to ensure smoothness
during engagement) is the brass, baulk ring type
(Borg- Warner) and is on the lay shaft for 1st and
2
nd
speeds, on the main shaft for 3rd, 4th and 5th
speeds and on the idler shaft for reverse gear (for
which there is no synchromesh).
This solution reduces gearbox noise when
stopped in neutral from the moment that 3 of the 5
pairs of gears are not driven.
The engagement and synchronization loads are
also reduced as a result of the corresponding
reduction in the inert rotating masses downstream
of the crankshaft.
The synchronizer on 1st and 2nd speeds, the
most used gears subject to the most stress, is the
double cone type requiring far less engagement
force compared with a single cone type traditional
synchronizer of the same size.
A new pre-synchronizer system comprising thrust
bearings is used on all the gears to improve
sliding and engagement: in 1st and 2nd speeds
the free (neutral) gears are supported by roller
chambers.
The geometry of the teeth and the kinematic chain
has been improved for the engagement of reverse
gear producing better maneuverability.
DIFFERENTIAL
The differential unit is located in the rear part of
the gearbox casing.
It comprises:
A crown wheel reduction
A differential housing in a single piece
which incorporates the planet and satellite
gears.
The differential is supported by two conical roller
Bearings. The planet gears have a splined internal
profile in which the two joints connected to the two
driveshaft’s that transmit the drive to the wheels
mesh. The speedometer idler drive gear is fitted
on the outside of the differential housing