Permanent xi o^ - library Info. Service 29 W. 39 st.. N. Y. PREPRINT: Subject to revision. Per- mission to publish this paper, in full or in part, after its presentation and with credit to the author and the Society may be ob- tained upon request. The Society is not re- sponsible for statements or opinions advanced in pa- pers or discussions at its Meetings.530099#96 VANTAGES AND 0 SADVANTAGES OF TRANMISSION IN By W. W. EDWARDS Supervisor, Truck Technical Service GMC Truck & Coach Division General Motors Corporation Pontiacp, Michigan Written discussion of this paper will be accepted at SAE Headquarters until August 1, 1953. Three double-spaced copies would be appreciated. For presentation at the SAE SUMMER MEETING The Ambassador and Ritz-Carlton Atlantic City, N. Jo June 7-12, ; SOCIETY of AUTOMOTIVE ENGINEERS, Inc., 29 West 39th Street, New York 18, N.Y. Downloaded from SAE International by Columbia Univ, Wednesday, December 05, 2018ADVANTAGES AMD DISADVANTAGES OF HTDRA-MATIC . IS TRUCK OPERATIONS For everyone who is even remotely connected with the truck transporta- tion industry, as well as those of us who depend upon it directly for our liveli- hood, the engineering advances which contribute to better motor trucks can lead to only one thing-— a higher standard of living with more dollars in everyone's pocket. Recently , we at GMG Truck have released an engineering advancement and product improvement that has already made its mark on the industry— and for which we see a very bright future. From the title of this paper, you, of course, know that I'm referring to the application of a completely automatic transmission to a truck~specifically, the appiication of the Hydra-Matic transmission to GMC light duty trucks. Before going into details, let's briefly describe the Hydra-Matic for those of you who may not already be familiar with it. Unlike torque converter type transmissions which depend on the flow and turbulent action of hydraulic fluid to multiply torque, the Hydra-Matic is a gear type transmission with four specific forward ratios and one reverse ratio, all used in combination with a fluid coupling. The gears used, are of the planetary type. The planetarys are hydrauiically controlled and operated with the four forward driving gear ratios obtained through various combinations of band and clutch application on two planetary sets. A third planetary set is used with the other two to obtain one reverse ratio . Power from the engine is transmitted through the fluid coupling which takes the place of a normal manually operated clutch. Now as you probably know, we at GMC have had the Hydra-Matic trans- mission as standard equipment in a package delivery truck for about one year. This model we call the PM150, and it has enjoyed wide acceptance in many dif- ferent operations—more of .which you will near later. In February of this year, Ifydra~Matic became availablie as an option in additional models having nominal ratings of 1/2, 3/4, and 1 ton, with various body types and wheelbases. Actual GVW's range from 4800 pounds to 8800 pounds, This gives the many light duty truck operators in numerous types of service an opportunity to benefit from the advantages of Hydra-Matic. Undoubtedly, you are familiar with the broad usage application? to which this transmission has been subjected— pass army wheeled vehicles, and also one of the toughest Operations imaginable-- successful motor coach city service. f0r about six- years. With such a background of successful operation in much more severe operating conditions than we are familiar with in passenger car usage, it is not unusual to find Hydra-Matic engineered for commercial truck application. ; .-..-. .. , . •, - ' ' \ ' ' -• -.. . ' - ' The questions I hope to answer for, you in this paper, which I'm sure most of you have in mind are; How did we do it, and why did we do it? Let's consider first, how we did it. In particular, there is one point on which our thinking should be clear. We