New Ford gearboxes and bigger
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A new family of all-synchromesh .vy-duty gearboxes, announced by the .d company today, comprises fourand speed versions of a basically similar box 1 an eight-speed range-change transsion. Cummins-powered tractive units I six-wheeled rigid chassis in the Ford ge will, in future, be powered by the nmins 504 V8 504 cu in. diesel, eloping 7 per cent more power than the ipany's 470 cu in. engine and 10 per t more torque. The vehicles are the tse II D Series.
kpplied to all the forward gears the chronizers of the new gearboxes are of baulk-ring type. Mainshaft gears are anted on needle-roller bearings, while the dwich casing is designed for easy 'icing. The boxes are suitable for vertical horizontal installation and provision is de for full-torque power take-off. Gears jected to high loads are made from 353 chrome-nickel steel and pairs of shing gears are matched during unbly. Improved lubrication is provided a helical scroll that is machined on the yard end of the mainshaft to give itive lubrication of the pilot bearing. n-t pegs of greater thickness than the ne keys of the mainshaft engagement :ve baulk any tendency for the gear to Li) out of. engagement under load. irbox casings are of cast iron and the ngs are split along the shaft axis to litate servicing.
Latios of the four-speed box, the 4-410-5, 6.49 to 1,3.21 to 1, 1.67 to 1 and Ito :verse being 7.18 to I. The six-speed box woduced in wide-ratio and close-ratio n. While the ratios of the wide-ratio box, 6-540-SW, are 9.19 to 1,5.51 to 1,3.13 , 1.87 to 1, 1.16 to 1 and Ito 1 (reverse 3 to 1), the close-ratio version (the )0-S) has ratios of 7.51 to 1,4.58 to 1, 2.85 to 1. 1.87 to 1, 1,31 to 1 and Ito 1, reverse being 7.18 to 1. The eight-speed range-change gearbox, the 8-570-S, has ratios of 10.71 to 1, 7.04 to 1, 4.93 to 1, 3.76 to 1. 2.84 to 1, 1.87 to 1, 1.31 to 1 and 1 to 1 (reverse 10.66 to 1), and it will be noted that the four upper ratios are similar to those of the six-speed close-ratio gearbox. While the 4-410-S has a torque rating of 300 lb ft (410 Nm), the 6-540-SW and 6-600-S are rated at 400 lb ft (540 Nm) and 440 lb ft (600 Nm) respectively, and the 8-570-S can accommodate an input torque of 420 lb ft (570 Nm).
The sixand eight-speed transmissions are designed to transmit the output of the largest engines fitted in Ford chassis, including the Cummins 504 V8. Six-speed gearboxes and the eight-speed version comprise a four-speed unit with an additional section at the rear in which the two extra pairs of gears required in each case are housed. The extension adds 7in. (180mm) to the length of the gearbox, both the sixand eight-speed types having a length of 17.2in. (437mm). Mounted vertically (as in the case of the Phase II models) the transmissions have a width of 14.2in. (360mm) and a height of 22.3in. (544mm).
Range-changes are controlled by a two-position switch on the gear lever and are power-operated by a compressed air cylinder, and interlock preventing the preselected gear in the main box from being engaged until the change has been completed. And a range-change cannot be made until the gear lever has been moved into neutral.
The existing Ford 4-310-S (formerly the T98A) four-speed gearbox remains in production as the standard transmission on vehicles powered by the 255 diesel, the new 4-410-S and 6-600-S being optional. While the 365 diesel is equipped as standard with the 4-410-S or 6-600-S, the 8-570-S is listed as an option. Vehicles powered by the 380 and Turbo 360 are fitted as standard with the 6-600-S and the 8-570-S is optional. Trucks having the Ford 511 or Cummins 504 V8 are fitted with the 6-600-S; the wide-ratio 6-540-SW combined with a two-speed axle and the 8-570-S are optional.
A three-plane gate layout is a feature of the six-speed gearbox, and each of the four gate positions of the eight-speed gearbox lever provides two ratios.
The greater swept volume of the Cummins 504 engine results from an increase in piston stroke of 0.25in. (6mm). Although maximum rpm is reduced from 3300 rpm to 3000 rpm, maximum output is increased from 185 bhp to 190 bhp. Gross torque is 360 lb ft at 1900 rpm and the torque produced at 1400 rpm is only 4 per cent lower at 345 lb ft.
In applications to the Ford 16-ton gvw four-wheeled rigids, the 504 is derated to 170 bhp at 3000 rpm and the peak torque is reduced to 325 lb ft at 1900 rpm, both outputs being the same as those of the original Cummins 470 cu in. diesel. In both forms the ratings comply with the BS A U141 standard.
Noise levels comply with the legal maximum of 89dBA, while 88dBA has been achieved as measured under BS 3425 and ISO test conditions. Fuel consumption has been improved to 0.392/0.425 lb bhp/h. A radiator with a 25 per cent greater area (625 sq in.) is fitted to vehicles powered by the 190 bhp version of the engine and cross-over flow is controlled by a modulating thermostat.
Other improvements include a crankshaft of higher-grade steel which gives an increase in strength of 20 per cent, while the compression ratio has been reduced from 17.5 to 1 to 17.0 to 1. The piston and piston-ring pack have been modified to improve piston stability and oil control. Cam timing has been changed to give high combustion efficiency, and a deeper sump is fitted that increases the capacity from 21 pints to 33 pints.
Under the revised system of chassis designation, the 16-ton four-wheeled rigid (powered by the 170 bhp version of the Cummins diesel) is known as the D1616 and the 24-ton six-wheeled tandem-axle model with the 190 bhp Cummins is called the DT2418. The 24-tons-gross tractive unit is designated the DA2418 while the 28-ton-gross model is known as the DA2818.