400 Commonwealth Drive, Warrendale, PA 15096-0001 U.S.A. Tel: (724) 776-4841 Fax: (724) 776-5760 Web: www.sae.org SAE TECHNICAL PAPER SERIES 2004-01-3026 Low-Speed Carbon Fiber Torque Capacity and Frictional Properties Test for ATFs Chris Morgan and Roy Fewkes General Motors Powertrain Tracy McCombs and Samuel H. Tersigni Afton Chemical Corporation J. Matthew Jackson Southwest Research Institute Reprinted From: Oils , Rheology, Tribology, and Driveline Fluids (SP-1894) Powertrain & Fluid Systems Conference & Exhibition Tampa, Florida USA October 25-28, 2004Downloaded from SAE International by University of Minnesota, Thursday, August 02, 2018All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise,without the prior written permission of SAE. For permission and licensing requests contact: SAE Permissions 400 Commonwealth DriveWarrendale, PA 15096-0001-USAEmail: permissions@sae.orgFax: 724-772-4891Tel: 724-772-4028 For multiple print copies contact: SAE Customer ServiceTel: 877-606-7323 (inside USA and Canada)Tel: 724-776-4970 (outside USA)Fax: 724-776-1615Email: Customer Service@sae.org ISSN 0148-7191Copyright © 2004 SAE InternationalPositions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE.The author is solely responsible for the content of the paper. A process is available by which discussions will be printed with the pap er if it is publishe d in SAE Transactions. Persons wishing to submit papers to be considered for presentation or publication by SAE should send themanuscript or a 300 word abstract of a proposed manuscript to: Secretary, Engineering Meetings Board, SAE. Printed in USADownloaded from SAE International by University of Minnesota, Thursday, August 02, 20181 2004-01-3026 Low-Speed Carbon Fiber Torque Capacity and Frictional Properties Test for ATFs Chris Morgan and Roy Fe wkes General Motors Powertrain Tracy McCombs and Samuel H. Tersigni Afton Chemical Corporation J. Matthew Jackson Southwest Research Institute Copyright © 2004 SAE International ABSTRACT Since the mid-1990’s, original equipment manufacturers (OEMs) of automobiles have been implementing torque converter clutches in automatic transmissions with a continuous, controlled slip mode, in order to improve the fuel economy of their vehi cles. These Continuously Slipping Torque Converter Clutches (CSTCCs) are prone to an undesirable phenomenon commonly called shudder. This phenomenon has been attributed to specific shapes or slopes in the friction coefficient versus sliding speed curve of the fluid/ clutch interface. Here, a method is explained that was developed to be able to screen fluids for shudder tendency, both in fresh and used states. Also included is a description of the reason for implementing CSTCCs, some background on shudder, and supporting data showing how the test method can distinguish between fluids that have different shudder tendencies. INTRODUCTION The introduction of CSTCCs provided a means of obtaining better fuel economy for cars equipped with automatic transmissions, including those vehicles equipped with lock-up torque converter clutches.[1-5] This feature, along with automatic transmission fluids (ATFs) that were far superior to their predecessors gave 2-10% better Corporate Average Fuel Economy (CAFE) numbers.[6-8] However, inappropriate fluids can cause CSTCCs to generate a drive line resonance that may present itself to the driver as vibrations and loud noises that can shake the entire vehi cle. This noise, commonly referred to as shudder, is a caused by the resonance of the converter clutch during the apply or release, which is a result of the frictional properties of the friction material/fluid/steel interaction on the CSTCC surface.[2,6] Many OEMs have included shudder detection in their factor