Search Results

New technologies are being commercialized across the automotive industry to address demands for improved fuel economy, emissions reductions, and improved customer satisfaction. Push-belt continuously variable transmissions (b-CVTs) are beginning to command a significant percentage of the market now dominated by manual and conventional automatic transmissions. In addition, automobile manufacturers plan to introduce the first traction drive toroidal-CVTs to the market place within the next five years. A review of the relative benefits and limitations of each of these automatic transmissions exists in the literature. In this paper we consider how the performance requirements of each of these automatic transmission systems impact automatic transmission fluid technology. The physical characteristics and screen test performance of two commercial ATFs, a b-CVTF, and two traction fluids were examined.

Chrysler began a limited development program directed toward a new automatic transmission fluid (ATF) early in 1989 and launched a full time effort in 1994. The development process for the new ATF involved a significant level of bench testing and eventually vehicle tests to evaluate the durability and shift quality of the ATF. The bench tests included those that pertain to oxidation and shear stability, anti-wear, frictional properties and torque converter shudder. Vehicle tests were primarily extended durability in both internal vehicle fleets and at external taxi sites. The mileage accumulated in this phase of the development program exceeded two million miles, all with no fluid drains out to 100,000 miles. Additionally, shift feel tests were conducted in Chrysler vehicles to verify compliance to targets. This paper summarizes the tests and results that lead to the development of the new Chrysler fill-for-life automatic transmission fluid.

Recent commercial specification revisions for automatic transmission fluids (ATFs) have focused upon more stringent friction requirements. More stringent friction durability characteristics are assessed using the SAE No. 2 tester. The commercial specifications do not include provisions to evaluate low speed friction characteristics, which have been shown to relate to torque converter shudder. This paper focuses upon effective use of the Falex 6 Multispecimen Tester to evaluate friction durability and to evaluate low speed friction characteristics in conjunction with low speed friction apparatus (LVFA) testing. Falex 6 testing agreed with torque fade observed in SAE No. 2 tests. Low speed stick-slip durability characteristics were effectively differentiated for a number of field ATFs. Falex 6 testing coupled with LVFA testing was shown to correlate with field experience and other test methods related to torque converter shudder.