Transmission Design

Southwest Research Institute (SwRI) operates one of the world's leading independent and fully integrated transmission design and development laboratories. SwRI provides engineering services and facilities for transmission and transaxle development. Since 1947, the Institute has helped improve conventional transmissions and develop innovative automatic, manual, and continuously variable transmissions for the automotive, agricultural, and construction equipment industries, as well as for the military.

Using sophisticated instrumentation, design and analysis techniques, and test facilities, SwRI automotive engineers design transmission systems that tolerate a wide range of operating loads and environmental conditions, while providing driver satisfaction and system reliability.

Institute engineers support all stages of transmission and transaxle design and development, including:

• Design
• Analysis
• Optimization
• Detailing
• Prototype fabrication
• Testing

Design

Using a wide array of proprietary and commercial software, SwRI engineers prepare models of transmission components and assemblies to illustrate innovative product design, develop novel concepts, and perform structural analyses. Institute staff members incorporate design changes as concepts evolve. SwRI designs a variety of transmission components, including:

• Transmission cases
• Planetary gear sets
• Clutch packs
• Differentials
• Pumps

Experienced machinists fabricate and assemble mechanical prototypes of SwRI-designed transmissions and components.

Analysis

Institute engineers use comprehensive analysis techniques to determine the stress capacity and strength of the transmission and to evaluate component interactions. Using the Finite Element Method for preliminary design, engineers evaluate new concept designs and improve production transmission components. SwRI uses analytical techniques that include:

• Linear static and nonlinear stress analyses
• Thermal analysis
• Clutch pack thermal analysis
• Computational fluid dynamics
• Modal analysis
• Noise, vibration, and harshness
• Torsional analysis
• Transient dynamic analysis
• Tribology

As part of its analytical procedures, SwRI uses rigid body dynamics to analyze loads that are subsequently evaluated with finite element analysis. Using kinematic and dynamic analyses, engineers investigate the dynamics of complex mechanical systems that involve large- and small-scale deformations.

An SwRI-developed finite volume-based numerical method uses unstructured brick and wedge elements to predict real-time friction material temperature.

Optimization

Structural optimization produces designs superior to conventional trial-and-error approaches. During initial design, optimization reduces the number of parts, manufacturing costs, and weight while increasing component functionality. In designing new transmissions, SwRI optimizes the following properties:

• Natural frequencies
• Stress and deflection
• Part thickness
• Material properties

Detailing

The Institute uses sophisticated software to produce detailed drawings from parametric models of transmission components and test fixtures. From these drawings, SwRI engineers fabricate and assemble mechanical prototypes of transmissions and their components, including:

• Automatic transmission
• Continuously variable transmission
• Chain transfer case
• Hybrid transmission
• Manual transmission
• Pumps
• Specialty gearboxes

Using industry-recognized procedures and Institute-developed test methods, SwRI minimizes transmission spin losses.

Prototype Fabrication

SwRI offers an extended range of rapid prototyping capabilities, including casting, forging, machining, and welding. Using state-of-the-art facilities and equipment, SwRI staff members develop prototypes of all mechanical and electrical transmission components, including:

Mechanical

• Gears, splines, and clutch drums
• Ferrite and nonferrite castings
• Transmission cases, pump housings, and bell housings
• Springs and gaskets
• Pistons and spool valves
• Toroids and sheaves
• Steel or aluminum oil pans

Electrical

• Wiring harnesses
• Printed wiring boards
• Electronic component assemblies
• Sensors
• Transmission control units

Testing

Flexible and well-equipped facilities allow the Institute to conduct a comprehensive range of transmission tests, including:

• Efficiency
• Performance
• Shift feel
• Fatigue
• Component testing

This brochure was published in November 1998. For more information about transmission design, contact Doug Fussner, Phone (210) 522-3972, Automatic Transmission Technology Section, Engine, Emissions and Vehicle Research Division, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Fax (210) 522-5720.

Engine, Emissions and Vehicle Research Brochures
SwRI Brochures SwRI Publications
SwRI Technical Divisions SwRI Home