High lubricant temperatures generated during the break-in of new differential assemblies has been of concern among original equipment manufacturers (OEM's). Many tests have been devised to measure the effects of speed, load and lubricant on the temperature generated in the axle. The major problem confronting the use of these tests has been a lack of repeatability and/or reproducibility. Recently, a European OEM axle lubricant break-in test procedure using a European sedan test vehicle has demonstrated highly repeatable and reproducible results. Test work had been limited to the European sedan. The applicability of the European OEM test procedure to a larger domestic U.S. vehicle was questioned. This paper discusses the applicability of the European test to a domestic sedan. Additionally, two other axle break-in test procedures were conducted using the same domestic sedan test vehicle. Three sulfur-phosphorus multi-purpose gear lubricants were evaluated. Comparison of lubricant response was made between test vehicles, test procedures and test facilities.