Commercial Heavy-Duty Power Transmission Fluids S. R. Sprague and J. E. Clevenger Wood River Research Laboratory, Shell Oil Co. THE PURPOSE OF THIS PAPER IS twofold: to familiarize the equipment designer with the performance characteristics of currently used heavy-duty (HD) power transmission fluids, and to compare the relative performance of these fluids. In discussions with various equipment manufacturers, we were frequently questioned regarding the performance fea­ tures of existing fluids. In attempting to answer these ques­ tions, we normally used data from test methods unfamiliar to the equipment manufacturer. A review of our test data showed that although we had substantial test information on each fluid, direct comparisons of different types fluids were limited. Allison Type C fluids were evaluated in the Type C specification tests, Ford Type F candidate fluids were eval­ uated against their respective specifications, and so forth. These experiences pointed up the existence of a language barrier between the oil industry and HD equipment manu­ facturers. A direct comparison of the various commercially used transmission fluids would act to provide a reference point since most manufacturers would have experience with one or more of these fluids. In order to facilitate a better under­ standing, me following sections compare the performance features of seven different types of commercial transmission fluids, as listed in Table 1. Additional information is also given in Table 1 regarding specification originator, field usage, availability, and approximate number of approved fluids. Several methods of comparison could be used to evaluate these fluids and it is difficult to choose test procedures which would be most meaningful. For simplicity, we have chosen to use the test methods or similar type tests as contained in the equipment manufacturers' lubricant specifications. A discussion of the significance of each test is also given. A listing of the various transmission fluid specification re­ quirements is given in Appendix A. Table 2 indicates the functional requirements which are discussed in the following sections and also the performance areas controlled by the individual specifications. It is emphasized that with some manufacturers, fluids which simply meet the listed specifica­ tions requirements are only accepted for additional evalua­ tion. Final factory approval in these cases depends on their evaluation in additional laboratory and proving ground type tests. The lubricants included in the following evaluation were selected to typify the better quality fluids which can be pur­ chased commercially and are representative of several dif­ ferent sources of supply. The quality level of fluids which meet a given specification can vary widely and in addition can possess widely different performance features not con­ trolled by the given specification. The choice of lubricant additive system is particularly important in regard to the later. For example, as previously reported (1)*, the per- * Numbers in parentheses designate References at end of paper. ABSTRACT The performance features of seven types of commercially used power transmission fluids are compared using test meth­ ods as required by the equipment manufacturers' specifica­ tions. These fluids fall within the SAE 10-20 viscosity grades and are used in the transmission, the hydraulic system, and, in some cases, the final drive. The significance of the various performance tests is also discussed. The overall data indi­ cate that some fluids can be combined into one to simplify oil supply problems inherent to mixed fleet operations. How­ ever, the continued need for specialty fluids is also apparent. Downloaded from SAE International by University of New South Wales, Monday, September 17, 2018formance features of the different additive packages used in the production of Type A, Suffix A, passenger car AT fluids can di