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A dynamometer test methodology was developed for evaluation of HMMWV axle efficiency with hypoid gearsets, comparing those having various degrees of superfinish versus new production axles as well as used axles removed at depot maintenance. To ensure real-world applicability, a HMMWV variant vehicle model was created and simulated over a peacetime vehicle duty cycle, which was developed to represent a mission scenario. In addition, tractive effort calculations were then used to determine the maximum input torques. The drive cycle developed above was modified into two different profiles having varying degrees of torque variability to determine if the degree of variability would have a significant influence on efficiency in the transient dynamometer tests. Additionally, steady state efficiency performance is measured at four input pinion speeds from 700-2500 rpm, five input torques from 50 - 400 N⋅m, and two sump temperatures, 80°C and 110°C.

For transmission suppliers tooled primarily for producing manual transmissions, retrofitting a manual transmission with actuators and a controller is business viable. It offers a low cost convenience for the consumer without losing fuel economy when compared to torque converter type automatics. For heavy duty truck fleets even the estimated 3% gain in fuel economy that the Automated Manual Transmission (AMT) offers over the manual transmission can result in lower operational costs. This paper provides a case study using a light duty transmission retrofitted with electric actuation for gears and the clutch. A high level description of the control algorithms and hardware is included. Clutch control is the most significant component of the AMT controller and it is addressed in detail during operations such as vehicle launch from rest, launch from coast and launch on grades.

The US Army is currently seeking to reduce fuel consumption by utilizing fuel efficient lubricants in its ground vehicle fleet. An additional desire is for a lubricant which would consist of an all-season (arctic to desert), fuel efficient, multifunctional Single Common Powertrain Lubricant (SCPL) with extended drain capabilities. To quantify the fuel efficiency impact of a SCPL type fluid in the engine and transmission, current MIL-PRF-46167D arctic engine oil was used in place of MIL-PRF-2104G 15W-40 oil and SAE J1321 Fuel Consumption In-Service testing was conducted. Additionally, synthetic SAE 75W-140 gear oil was evaluated in the axles of the vehicles in place of an SAE J2360 80W-90 oil. The test vehicles used for the study were three M1083A1 5-Ton Cargo vehicles from the Family of Medium Tactical Vehicles (FMTV).

In recent years there has been an increased interest in the continuously variable split power transmissions as these drive units are capable of vehicle launches and directional changes without using clutches. These tasks are accomplished by appropriately splitting power between the fixed mechanical and variable ratio branches. The power is recombined at the transmission output. A properly designed split power transmission arrangement will improve vehicular agility and reduce variator size. This paper provides characteristics of six single stage input coupled continuously variable toroidal split power transmission arrangements. Mathematical equations are derived for speed, torque and power. A computer program that utilizes the capabilities of Matlab is developed. The program calculates the required fixed and variable branch gear ratios for the predefined variator, planetary and overall transmission ratios.

Conventional methods for determining automotive powertrain efficiency include (1) component-level testing, such as engine dynamometer, transmission stand or axle stand testing, (2) simulations based on component level test data and (3) vehicle-level testing, such as chassis dynamometer or on-road testing. This paper focuses on vehicle-level testing to show where energy is lost throughout a complete vehicle powertrain. This approach captures all physical effects of a vehicle driving in real-world conditions, including torque converter lockup strategies, transmission shifting, engine control strategies and inherent mechanical efficiency of the components. A modern rear-wheel drive light duty pickup truck was instrumented and tested on a chassis dynamometer. Power was measured at the engine crankshaft output, the rear driveshaft and at the dynamometer.

This paper presents a general discussion of automatic transmission parasitic losses and efficiency characteristics. Efficiency characteristics of the three major automatic transmission components-pump, torque converter, and gearbox-and their contribution to the transmission total torque losses are examined. A data reduction method for isolating gearbox torque losses from total transmission losses is also described. The information presented is based on pump, torque converter, and transmission testing performed at SwRI for Ford Motor Company. Test data was used to perform analytical fuel economy benchmarking studies. Testing included 13 transmissions manufactured by American, European, and Japanese manufacturers for 3.0-5.8L truck applications.

Increased concern for improving fuel mileage in today's vehicles has focused attention on powertrain component efficiencies. Currently, no efficiency standards exist for automatic transmissions but, uniform testing procedures do exist. Consequently, vehicle and transmission manufacturers have no basis for comparing transmission-to-transmission performance. In addition, manufacturers have no design targets from which to critique their product. This paper addresses this issue by developing an overall transmission efficiency rating. This rating is based upon average transmission operational torques and speeds, the percent time of operation in each gear for a representative duty cycle, and representative efficiencies at these conditions based on test data obtained from a cross section of current production transmissions.

An Automatic Tire Inflation System (ATIS) specifically designed for commercial use on trailer axles is currently being installed and utilized successfully by trucking companies, the military and owner/operators throughout the U.S. A need exists for an ATIS specifically designed for the drive axles of Class 8 over-the- road tractors. The addition of an ATIS for drive axles will expand automatic tire monitoring capability to all heavily loaded tires of the over-the-road truck/trailer rig. An ATIS for drive axles has been designed, fabricated and tested. Testing and evaluation of the prototype ATIS drive axle system indicates the system can be successfully installed on a typical tractor rig and operated for an extended period without problems. The testing included a 50,000 mile evaluation of the ATIS installed in a laboratory test fixture. The test fixture used stock axle parts and operated at 65 MPH. Environmental testing was conducted at temperatures ranging from -20 to +200 degrees F.

For many years the SAE No. 2 friction machine has been used to measure the coefficient of friction obtained through the interaction of fluid, steel and clutch material. In addition, by forcing energy through the wetted clutch-steel interface and measuring the decay of the coefficient of friction over time, the durability of the materials and fluids can be determined. This paper discusses the use of a numerical computer model to duplicate SAE No. 2 data. The inputs for this model include test stand geometry and physical properties as well as output from a low velocity friction apparatus (LVFA). The LVFA uses a small disc of friction material, a small disc of steel material, and a small sample of fluid to generate a coefficient versus speed curve (m vs v). It was found that torque traces and speed traces generated by this model correlate well with actual SAE No. 2 data. THERE ARE SEVERAL REASONS for creating this model.

Next generation vehicles are under environmental and economic pressure to reduce emissions and increase fuel economy, while maintaining the same ride and performance characteristics of present day combustion engine automobiles. This has prompted researchers to investigate hybrid vehicles as one possible solution to this challenge. At Southwest Research Institute (SwRI), a unique parallel hybrid drivetrain was designed and prototyped. This hybrid drivetrain alleviates the disadvantages of series hybrid drivetrains by directly coupling the driving wheels to two power sources, namely an engine and an electric motor. At the same time, the design allows the engine speed to be decoupled from the vehicle speed, allowing the engine to operate at its most efficient state. This paper describes the drivetrain, its components, and the test stand that was assembled to test the parallel hybrid drivetrain.

A multi-mode hybrid hydromechanical transmission (HMT) with infinite variability is designed to meet the power transmission needs of medium duty on- and off-road vehicles. A hydraulic pump-motor assembly provides output speed and torque variability in an input coupled split power configuration. Dual planetary arrangements with two multiplate clutches allow multi-mode ratio change and combination of power from the mechanical and variable branches of the power path. Hydraulic accumulators offer hydraulic power assist during launch conditions and storage of reclaimed energy during braking events. Transmission kinematic, force and power flow analyses will be developed for the HMT and analyzed for suitability in a bus application. The resulting benefits and areas for improvement will be discussed.