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The purpose of this paper is to demonstrate the differences in braking capability of the different types of tires through data collected from single variable testing. The only variable in these tests was the type of tire installed. Three different tire types; summer, all season, and winter, all of the same size, were tested in moderate ambient temperature on wet and dry asphalt surface with a single vehicle. The braking tests were conducted with ABS actived and deactivated for modulated and locked wheel friction comparison of the tire types. Accident reconstructionists rely on accurate friction coefficients to calculate speeds from skid and yaw marks left at a collision scene. Maximum effort braking performance, whether locked wheel or ABS modulated, is influenced mainly by the road to tire interaction and is affected by the type of tire. High performance, “Summer”, tires are increasingly available as Original Equipment Manufacturer fitment.

In the United States most passenger vehicles have an automatic transmission with a transmission shifter position labeled Park. When the transmission shift selector is placed in Park, a parking pawl (a pivotally mounted arm) engages a parking gear on the output shaft to immobilize the drive shaft and prevent the vehicle from moving. The driver also has the option of engaging the parking brake with a lever, pedal, or button to immobilize the vehicle. Many state driver's license manuals and vehicle owner's manuals commonly suggest the use of the parking brake every time the driver exits the vehicle regardless of the transmission type. Testing is performed by vehicle manufacturers on the automatic transmission to insure the Park shift position pawl holds the vehicle on steep slopes. This study was conducted to investigate how often and why drivers use the parking brake.

Major revisions for a 2004 model year Sport Utility Vehicle (SUV) included body, suspension, mounting systems, NVH package upgrades, and drivetrain including a new transfer case - the Magna Drivetrain NP244-Gen2 (2nd Generation). During vehicle development, an objectionable level of transfer case chain whine was experienced over a narrow speed range. From vehicle and component testing, the noise was determined to be a transfer case to vehicle systems integration issue excited by the transfer case chain mesh order. The noise issue was solved through passive noise cancellation using a Gemini HyVo® phased sprocket and chain set. The half-pitch phasing of the sprocket and chain pair resulted in near total elimination of the fundamental chain mesh frequency. The NP244-Gen2 is the first transfer case to utilize a phased chain and sprocket system resulting in a best in any class performance for transfer case chain mesh noise.

Different methodologies to test transfer case imbalance were investigated in this study. One method utilized traditional standard single plane and two plane methods to measure the imbalance of the transfer case when running it on a dynamic balance machine at steady RPM, while a second method utilized accelerometers and a laser vibrometer to measure vertical vibration on the transfer case when running it on a dynamic balance machine in 4 Hi open mode during a run up from 1000 to 4000 RPM with a 40 RPM difference between the input and output shaft speeds. A comparison of all of the measurements for repeatability and accuracy was done with the goal of determining an appropriate and efficient method that generates the most consistent results. By using the traditional method, the test results were not repeatable. This may be due to the internal complexity of transfer cases. With the second method, good correlation between the measurements was obtained.

Two vehicle level test methods were developed that illustrate the relationship between 1st order noise in a cabin, and driveline imbalance contributors. At the launch of a new 2005 4WD sport utility vehicle program, a significant boom noise complaint was observed on many vehicles between 55-70 mph. The full time, electronic actively controlled, torque biasing transfercase was intensely reviewed as a potential source of excessive torque induced imbalance. Testing of the transfercase was performed on imbalance measurement stands, dynamometers, and in the vehicle. The result was the identification of two issues. First was that two internal to the transfercase parts were found to have excessive runout. Second was that there was a lack of vehicle correlation to transfercase imbalance. An extensive effort involving over 50 vehicles of the same model was pursued to find the source of the problem.

Gear whine is a fundamental issue associated with the design of automotive transmission gears. The evaluation of gear whine has long been a subjective rating. The goal of this paper is a comparison of the objective data and the subjective rating system. Objective analysis can not always replace the subjective evaluation completely, but it can induce a consistency that subjective rating lacks. An objective analysis method of in-vehicle gear whine order tracked data subtracted from the overall noise level over a rpm range is compared to subjective rankings to establish an objective rating. A correlation and statistical analysis of the objective data has proven effective in evaluating the noise performance of gear whine in a vehicle. There is a concern for the acoustic performance of the gears in a transmission and a consistency in the evaluation, due to the ever increasing customer awareness of noises in automobiles