In this study, thermal characteristics of an automotive rear axle assembly are investigated experimentally in conjunction with the corresponding spin and mechanical power losses. For this purpose, a rear axle is instrumented at multiple critical locations via thermocouples. In addition, for assessing the impact of any changes in preload of the pinion bearings on axle efficiency, a proximity probe system is designed and implemented to measure the relative displacement of the pinion shaft with respect to the differential carrier. A multi-channel data collection and analysis system is devised to collect and process all of the data including thermocouple signals from stationary sensor locations, thermocouple signals from rotating pinion and gear sensor locations via two separate telemetry systems, the proximity probe signal, and the torque-meter signal(s).
The instrumented axle and its data acquisition and analysis system are operated under unloaded, variable temperature conditions to quantify the changes in temperature in relation to the spin power loss. In addition, results of tests under loaded and unloaded conditions with constant oil temperature are also presented to relate the measured power losses to the state of axle temperatures and pinion preload.