It has been recognized for many years that multipurpose axle lubricants give rise to much higher axle break-in temperatures than lead-soap, active-sulfur or sulfur-chlorine-lead lubricants. Evaluation of differences in axle lubricant break-in temperature between the various multipurpose gear lubricants has been complicated by lack of repeatability and reproducibility.
The work described in this paper shows that one of the most important variables affecting axle break-in temperature, under the conditions of the test technique used, was torsional axle preload and that control of dimensional preload in itself is not sufficient to ensure good test repeatability.
The test technique described here has been used to evaluate the axle lubricant break-in temperature properties of several sulfur-phosphorus multipurpose gear lubricants. The technique has been shown to be highly repeatable and reproducible when temperatures are compared at normalized variables of ambient temperature and torsional axle preload.
This paper is primarily limited to a study of the axle break-in temperature behavior of a Volvo sedan equipped with an integrally built rear axle, driven at or below the maximum weight limitation imposed by the manufacturer.