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Switch to range change
Page 44
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for ZF by Gibb Grace
New 'heavy' gearbox will suit 360 bhp engines
• Following the announcement last week that ZF, the German gearbox manufacturer, has formed a new British company to handle sales and service of its products comes the news that the company is introducing the 5S-110GP gearbox and WSK torque converter to Britain. The first units for appraisal are already in the hands of some vehicle manufacturers.
The gearbox has been specifically designed to suit the 300-360 bhp engines currently used to power the latest 38 tonne European vehicles. It is used, for example, in the Mercedes-Benz LP 1632 truck behind the 320 bhp V-10 400 series engine (see road test, CM April 23 1971).
The design features a basic four-speed gearbox with crawler and reverse gears and a rear-mounted transfer unit of the planetary gear type. The planetary gears double the ratios of the four-speed box so that together with the crawler speed, nine forward speeds are available. The gearbox is available in constant-mesh form designated 5K-110 or in syncromesh form designated 5S-110. The simplest form of the new gearbox, that is the type with co-axial input and output shafts, weighs approximately 660Ib in constant mesh form and 6851b in synchromesh form.
The same basic versions, 5K-110GP and 5S-110GP, have a crawler ratio of 13.1 to 1 and eight further ratios of 8.67, 6.37, 4.65, 3.43, 2.53, 1.86, 1.36 and 1.0 to 1; reverse is 16.2 to 1.
The gearbox is of the range-change type unlike previous ZF boxes and uses a basic H-gate pattern. Gears 1 to 4 are in the normal position in the gate and having operated the range-change switch incorporated in the gear lever knob these positions are used again to get gears 5 to 8. Reverse and crawler gears are positioned to the left of the H-gate with reverse next to first and crawler next to second gear.
The range-change planetary gear is selected pneumatically and an automatic blocking valve prevents a change taking place when one of the basic gears is selected and ensures that a change can be made only when the basic four-speed box is in neutral.
The synchromesh box 5S-110GP is equipped by a further electronic-pneumatic engine overspeed safety device consisting of two independent interlocks, a gate interlock and a range-change interlock. The gate interlock blocks the shift movement of the selector lever from gear positions 3 /4 to 1 /2 or from 7/8 to 5/6. The interlock blocks a range change to the low range above a specified road speed. Solenoid valves controlling these interlocks are themselves controlled by signals from an impulse transmitter giving the gearbox output speed.
The locking speeds are designed so that during down-changes from 7th, 5th and 3rd gears only the permissible maximum engine speed of the next lower ratio can be reached. Down changes 8-7, 6-5, 4-3 and 2-1 are not interlocked.
When the gearbox is used correctly these interlocks are not noticeable to the driver but they do come into action if an incorrect ratio is selected. The respective gate or range-change lock remains in operation until the travelling speed is correct for the chosen gear and thus prevents over-revving of the engine.
This new gearbox has been designed to be used in conjunction with the WSK (Wandeer-Schaltkupplung) torque converter and clutch announced earlier by ZF (CM Dec 1 1972) and in this form can be matched to engines of up to 450 bhp output. ZF sees the synchromesh box and torque converter as a next natural step in heavy vehicle transmissions and points to the advantages of wear-free starting even under difficult conditions, favourable efficiency and fuel consumption due to the automatically controlled lock-up clutch in the converter, fewer gear changes and protection of the drive line. Unlike some torque converter installations the WSK model allows full engine braking to be used.
Ford sales up
• Sales of Ford commercial vehicles hav( increased by 16 per cent during the firs five months of this year compared vvitl the same period last year. A total o 42,500 units were sold compared witl 36,732 units for the first five month last year. Escort van sales are up 2r per cent, Transit sales up five per cen and D series truck sales up 32 per cent.
Foden depot closes
• Fodens' Bletchley depot is closing fror today (Friday) and will no longer b offering Foden service. Service in the area i being taken over by Warringto Commercial Vehicles Ltd, Lower Woottor Boars Hill, Oxford (tel Oxford 73904).