The Engineering Society For Advancing Mobility and Sea Air and Space, INTERNATIONAL^ 400 COMMONWEALTH DRIVE, WARRENDALE, PA 15096-0001 U.S.A. Development of a Sprag Wear Test Procedure for Evaluating the Antiwear Performance of ATF's Frank Caracciolo General Motors Research Laboratories International Fuels and Lubricants Meeting and Exposition Tulsa, Oklahoma October 22-25,1990 Downloaded from SAE International by University of New South Wales, Sunday, August 19, 2018The appearance of the ISSN code at the bottom of this page indicates SAE's consent that copies of the paper may be made for personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay a $5.00 per article copy fee through the Copyright Clearance Center, Inc., Operations Center, 27 Congress St., Salem, MA 01 970 for copying beyond that permitted by Sections 107or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Customer Service Department. To obtain quantity reprint rates, permission to reprint a technical paper or permission to use copyrighted SAE publications in other works, contact the SAE Publications Group. SAE GLOOM YOBlLm DATABASE No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior writ- ten permission of the publisher. ISSN 01 48-7191 Copyright 1990 Soclety of Autornotlve Engineers, Inc. Positions and opinions advanced in this paper are those of the Persons wishing to submit papers to be considered for presen- author(s)and not necessarily thoseof SAE. The author is solely tation or publication through SAE should send the manuscript responsible for the content of the paper. A process is available or a 300 word abstract of a proposed manuscript to: Secretary, by which discussions will be printed with the paper if it is Engineering Activity Board, SAE. published in SAE Transactions. For permission to publish this paper in full or in part, contact the SAE Publications Division. Printed In USA Downloaded from SAE International by University of New South Wales, Sunday, August 19, 2018Development of a Sprag Wear Test Procedure for Evaluating the Antiwear Performance of ATF's Frank Caracciolo General Motors Research Laboratories ABSTRACT A sprag clutch wear test procedure for evaluating the antiwear performance of automatic transmission fluids (ATF's) has been developed using a bench test apparatus. The wear test procedure provides an effective screening tool for incorporation into Automatic Transmission Service Fluid Qualification Test Procedures and Specifications. Two, widely-used ATF's provided reference data for wear comparisons and seven ATF candidates were evaluated for their antiwear performance. In addition, an additive-free, mineral-oil base stock was tested to highlight the need for fully-formulated fluids in automatic transmissions. Surface texture analysis complemented the weight-change data which was used as the primary wear criterion. Supplemental tests which examined sprag components at various intervals throughout the test period provided sufficient data to suggest a possible mechanism for wear initiation and propagation in the sprag clutch. THE ORIGINAL CONCEPT of the sprag clutch had been developed in the late 1940's. The chief attribute of this one-way clutch design was its high, load- carrying capacitylsize ratio relative to a roller clutch. Because of torsional de-phasing problems, sprag clutches were not utilized extensively until the early 1950's when a full-phased design became available. Since that time, sprag clutches have been used in many automatic