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Automatic gearshift for Renaults

31st October 1991
Page 11
Page 11, 31st October 1991 — Automatic gearshift for Renaults
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Which of the following most accurately describes the problem?

• Renault has introduced an automatic gearshift system for its AE and R heavy trucks.

The TBV (telecommande de boite de vitesses) has been developed by Renault engineers for the company's standard B18 synchromesh transmission.

It works along the same lines as Scania's CAG system, using a computer to pre-select the most appropriate ratio, and Renault claims TBV can reduce fuel consumption and clutch wear as well as improve driver comfort.

UK availability is scheduled for next year, with a price tag of about £3,000. The system has been tested over four years in 20 vehicles driving some 10 million kilometres. TBV uses the conventional manual gearbox, fitted with pneumatic actuators rather than a mechanical linkage.

A digital display on the instrument panel indicates the gear that the system recommends, and if the driver agrees, that ratio can be engaged by using the clutch normally.

A buzzer sounds when the change is complete.

The control system has two modes, "economy" and "performance", and depending on which is selected, chooses the next ratio to use the engine in its maximum torque or maximum power speed band.

If the driver wishes to select an alternative ratio, or change the mode, this can be done using the "gear lever".

The system requires no specific maintenance, and has a self-diagnostic facility. The claimed savings on running costs include an average fuel saving of 1 lit/100km for fleets by narrowing the gap between "good" and "bad" drivers, and extended clutch life.

A short drive in a laden AE 380 fitted with TRY gave a favourable impression, despite a lack of familiarity.

The computer could be left to select the next ratio in normal conditions, leaving the driver to concentrate on the road and dip the clutch at the appropriate moments. At all times, the digital display on the dash showed the recommended ratio, the mode, and the gear engaged.

Experimenting showed that the chosen ratio could be adjusted up or down by moving the lever fore or aft, and high or low split could be selected using a button on the side of the lever.

The speed of gearchanging appeared to be little different to a manual shift, although this was hard to gauge as the "bleep" to indicate that a gear was engaged was rather difficult to hear.

Although TBV certainly means less work than Renault's normal double-H shift, we would need to try it over a longer distance, and more especially over some demanding terrain, to be able to judge the real merits of the system.

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