Leyland's 02 gives jerk-free changes
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by Martin Hayes
FULL DETAILS have been released by British Leyland of its new G2 fully automatic control unit for fivespeed automatic transmissions which is currently being assessed on Leyland Nationals, Leopards and Atlanteans in London, Manchester, Liverpool and Dublin. The G2 system is said to be showing advantages in performance and economy over existing electronically controlled epicyclic transmissions while initial running costs compare favourably with torque convertor transmissions.
The 02 is claimed to offer marked improvements over previous automatic control systems produced by British Leyland in the past. The most recent of these, the Self-Changing Gears C-83, can be applied to wide-ratio four-speed boxes without "kickdown" range-change and is essentially a "bolt-on" attachment which converts semi-automatic gearboxes to fully automatic operation.
However, the 02 is fully integrated with the gearbox and incorporates both kickdown and a jerk-free gear shift quality, it is claimed. A Leyland National fitted with the G2 device was tested in CM, March 22. The device is expected to be offered as an option on all LNs from the end of the year. No price is yet available.
Throttle dipping
Smooth upward gear changes are ensured by automatic simulation of the "throttle dipping" exercise employed by most drivers. This technique is used to improve speed synchronization and involves an electro-pneumatic valve and slave ram acting on the fuel pump which is triggered by a signal from .a translator unit. The translator is essentially the brain of the control system and it interprets the incoming signals from the gear selector, speed signal generator and performance level switch.
The translator then feeds out control instructions to the transmitter. In the maximum performance condition, full throttle changes take place near to maximum engine speed in the appropriate ratio to achieve the best vehicle performance. Under all other conditions the gear shift permits a change in order to obtain higher gears earlier for im proving normal town running economy.
Synchronization
On down-shifts neutral gaps are provided for synchronization — thus smoothing down shifts while under power and when coming to rest. Interlocks prevent instantaneous shifts from forward to reverse gears at speed and also to maintain the particular gear in use should any failure occur. This is claimed to prevent engine over-speeds and possible injuries to passengers which would otherwise occur with inadvertent down-changes. A warning light indicates failure to the driver.
Essentially, the transmission is both road speed and load sensitive. It is claimed that this facility pre vents embarrassing situations where the transmission would otherwise tend to change up when the , power demand is reduced. Careful matching of the control unit to the power pack response avoids this condition, it is claimed.
Facilities provided by the G2 include a two-level gear shift performance brought about by a simple accelerator "kickdown" switch and manual override positions in third and fourth gears.
The brain — or translator unit — is made up of colourcoded, separate, encapsulated modules which are said to be easily understandable by relatively untrained personnel. These plug-in modules are also designed to minimize breakdowns and in the event of failure the colour coded socket configuration makes replacement simple. Transparent covers over the relays allow quick fault-finding, The G2 system is said to offer a level of sophistication in automatic trans mission control which is unique. It is suitable for integration into power shift gearboxes of both pneumoeyclic and hydrocyclic types.
SAB brake adjuster
GREYHOUND Bus Lines Inc are fitting their vehicles with SAI3 automatic brake slack adjusters and not as stated in CM, April 12. The unit, marketed in the States by Borg and Beck, is similar to that fitted to all Leyland vehicles with S-cam brakes.