Measurements have been made of some of the parameters affecting energy losses in back axles and gearboxes. The work was mostly carried out on a dynamometer but a limited number of track tests were used to corroborate the test rig results. The axle and gearboxes tested were standard Ford Transit units. There was a large change in axle efficiency with oil temperature, efficiency improving with increasing temperature. Under low temperature, high viscosity conditions, power loss in the axle increased approximately linearly with rotational speed and efficiency improved as transmitted power increased. However even under high power, low viscosity conditions the axle absorbed at least 6 per cent of the power transmitted and under low power, high viscosity conditions the power loss was as high as 40 per cent of transmitted power. Gearbox efficiency was generally above 90 per cent, however tests with a Ford Transit van on the test track showed that efficiency changes are significant in terms of fuel consumption. (A)

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