The extremely compact and reliable clutch-gearbox-differential
unit is the result of new design concepts. This unit is
mechanically fixed to the engine and to its support frame.
The transverse arrangement, in line with the engine, results in silent operation, engagement precision and high maneu- verability.
The single disc hydraulically controlled dry type clutch is fully adequate to the high torque transmitted to the clutch disc. The low pressure needed to operate the clutch pedal is the result of an innovative operating geometry of the disc pressure plate and of a particular attachment of the hidraulic control therefore, a quick and precise engagement is assured, which is essential on a sporting vehicle like the 164.
The clutch disc slack take-up is performed automatically by the hydraulic control system, which maintains the thrust bearing in contact with the disc pressure plate; the result of this feature is a maintenance-free clutch.
The hydraulic control circuit uses the same fluid as the brake system.
The new anti pollution clutch disk (free of asbestos) provides and excellent friction~coefficient and high wear resistance, a guarantee of reliability and long life. Gearbox~ifferentlal and hydreulic control clutch - crose section view
The gearbox is tranversally arranged.
All speeds are synchronized; the synchronizers of higher speeds are installed on the gearbox main shaft to reduce the inertial moments during the synchronization phase.
The above feature also reduces the gearbox noise, particularly at idle speed.
The gears are a very close ratio to better appreciate the sporting character of the engine.
The dual-rod speed shifting mechanism assures absolute precision. The mechanism consists mainly of a short shift lever with ergonomic knob, a speed engagement rod, and a reaction rod.
The differential, integrated inside the gearbox, is driven by a
cylindrical reduction pair with helical teeth that provide high
mechanical efficiency and silent operation.
Specifically designed forks which lock onto more than half of the shaft circumference prevent any speed jamming, and provide high precision of speed engagement.
For this front wheel drive vehicle, the transmission has been designed in a special way to withstand the high engine power.
An intermediate shaft fitted on the right side of the differential
allows the use of two axle shaft of the same length, and
prevents dangerous asymmetric loads on the steering wheel.
The ball crown type homokinetic couplings transmit the high
engine power with absolute safety and quietness.
The automatic transmission of the 164 has been specifically designed for this new front wheel drive-transversally mounted engine vehicle.
Four forward speeds, and reverse, provide flexibility to meet any driving conditions, and best use of the high engine output power and torque.
The above solution results in a remarkable improvement in the transmission efficiency, which is normallytheweakpoint of traditional transmissions.
The final reduction ratio has been calculated so as to
provide brilliant performance in terms of speed and acceleration,
according to the sporting tradition of Alfa Romeo
vehicles.
The gearbox consists of:
The torque converter dynamically connects the engine to the gearbox and, in some conditions, It increases the available torque.
The torque increase is proportional to the difference between the converter inlet and outlet speeds. For example, the available torque is twice the engine output torque when the vehicle is stationary, while there is no torque increase during normal operation of the vehicle, and the torque converter simply acts as an hydraulic coupling.
Due to the absence of direct contact between rotating parts, the torque converter is not in practice subject to wear, with great advantages in terms of reliability and life.
Automatic speed shifting is performed through the hydraulic engagement of disc clutches and brakes, which provides a very smooth speed shifting.
The automatic transmission oil cooling system (thermostat and radiator) provides proper dissipation of heat produced in the transmission, with evident advantages in terms of efficiency and reliability.
The kick-down device enables shifting to the lower speed by simply applying full acceleration, thus achieving a fast abd safe acceleration which is essential when passing or in other similar instances.
The differential is the same compact and reliable unit installed on the manual transmission versions.
The speed selector lever enables the driver to select the speed which more suits his driving style or driving conditions (maximum economy, sport driving,motorway, uphill, downhill, etc.).
In other words, the driver can exploit the advantages of the automatic transmission without renouncing the exclusive pleasure of driving an Alfa Romeo.
Both front and rear suspensions are of the independent type with Mc Pherson type telescopic shock absorber and helical springs.
Prolonged testing on any type of road surface enabled the optimization of the geometries and settings which results in the best combination of road holding and driving comfort. The fiont sUspension is mounted onto the lower side of engine support frame by means of a rugged triangular arm.
The off-line assembly of this Item provides the highest precision to the whole front geometry, and facilitates the suspen- sion setting and maintenance.
Furthermoe the compactness and high rigidity of the structure helps to maintain the geometry through the life of the vehicle.
The thelescopic shock absorbers are out of alignment with
respect to the wheel centerline; this feature allows to lower
their attachment point, and provides great advantages in
terms of vehicle's aerodynamics.
The rear suspension is mounted onto a pre-assembled cross frame that provides the same advantages in terms of geometry and setting as for the front suspension.
The rear suspension includes dual cross rods and dual longitudinal stmts which maintain the wheels parallel to the vehicle's longitudinal axis, thus enabling perfect control of shocks and high road holding.
The stabilizer bar minimizes the "rolling" effect during turns, and gives the vehicle exceptional stability.
On the "S" versions, an advanced electronic system varies
in real time the setting of the shock absorbers to suit different
road surfaces and driving conditions.
The design of a suspension always aims to the best combi- nation of "rigid" behavior (which increases the road holding) and "soft" behavior (which increases the comfort).
Alfa Romeo have developed a new suspension control system that gives this design problem an optimal solution. The setting of the four shock absorbers can be varied in real time to suit different road surfaces and driving conditions.
Two suspension settings are available:
A system, therefore, coherent with the traditions of Alfa Romeo,
and that provides simultaneously the best of sporting,
safety, and comfort characteristics.
An electronic control unit, on the basis of signals provided by sensors varies the suspension setting by means of four solenoid valves which meter the oil flow inside the shock absorbers.
The suspension is set to the rigid mode when any of the sensors alerts the elctronic control unit of unusual road or driving conditions such as:
The setting is rigid at very low speed to prevent excessive springing during manoeuvres.
The simplicity and realibility of the system, along with a very
short intervention time, provide an immediate response to
different driving conditions.
The brake system has been designed to suite the high performance of this top class vehicle, and provides a high level of safety in most any circumstance.
The system consists of a crossed dual hydraulic circuit, four brake discs (self-ventilated on the front) and floating brake calipers. The brake pads are protected to avoid contact with foreign matter and dirt.
The design of the hydraulic circuit aimed to provide the maximum safety.
Even in the event of an accident with consequent damage to a brake line, the braking of a front wheel and of an opposite rear wheel is assured.
Oversized brake discs provide a wide friction surface and quick dissipation of heat.
A vacuum servo unit assists the pressure applied on the brake pedal.
A load proportioning valve on the rear axle further improves
the brakes reliability in any loading condition.
The vehicle's active safety is further increased by the latest in A.B.S. technology, which provides control of the vehicle and maximum tire grip even in panic braking and reduced road adherence (ice, snow, etc.).
This system, fitted on the most prestigious American and European cars, is very, reliable: all of its components have been tested by a strict quality control procedure.
Experimental testing has determined the behavior of the vehicle during braking with different type of tires and surface conditions: it was noted that the maximum braking action is provided when a certain degree of tire slippage is reached, and suddenly decreases when this value is exceeded. The A.B.S. actuates right at this point, and provides the most effective braking action which can be obtained for the existing tire and road conditions.
The A.B.S. fitted on the 164 is of the four channel type; each
wheel is independently monitored by a channel, thus enabling
the best directional control of the vehicle during braking.
The main components of the A.B.S. are:
The solenoid valves, when actuated, reduce the pressure of fluid delivered to the brake caliper of the wheel which is near locking; the pressure is adjusted so as to obtain the maximum braking action and avoid wheel lock-up.
The A.B.S. is integrated in the conventional brake system,
with evident advantages in terms of simplicity and reliability.
Normal operation of the powerful and reliable bra~e system
is assured in the event of an A.B.S. malfunction.
The system consists of a belt driven pump which delivers pressurized fluid to the rack to assist in steering action.
The steering rack shape provides a variable assist as a function of engine revolutions: maximum assist when the vehicle is stationary to facilitate manoeuvering, reduced assist at high speeds to provide precise and sate steering.
In the event of a malfunction, the steering is always assured by the mechanical linkage.
The installation of the steering rack behind the drive train,
and the articulated steering column, improve the vehicle's
passive safety in the event of a frontal collision.
