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A simple ADAMS model was developed for simulating one possible mechanism that causes low-frequency (less than 1 kHz) noise in disc brake assemblies for heavy-duty and medium-duty trucks. The model consists of: truck tire, axle housing, torque plate, caliper, push rods, inner pad, outer pad, and rotor. Only one component (the torque plate) was modeled as a flexible body (using a finite element model), while all other parts are considered as infinitely rigid. A lumped parameter representing the suspension wrap-up stiffness resists the axle pitch motion. When the brakes are not engaged, the system has two distinct modes of vibration, namely, the axle pitch mode which is governed by the suspension wrap-up stiffness, and the caliper transverse (side-to-side) mode, which is governed by the stiffness of the torque plate (out-of-plane deflection of the torque plate) and by the suspension lateral stiffness.

Since 1983 the Torsen® differential has been employed in the powertrain of more than two-dozen sedans, SUVs, and military vehicles. This differential device is renowned for its unique high torque bias capacity. Torque bias has long been recognized as a desirable drivetrain characteristic that enhances both a vehicle's drivability and stability. Since the generation of torque bias relies on friction, the know-how in achieving balanced design of torque bias and efficiency is crucial. Presented in this paper is an analytical evaluation of the performance of Torsen differential with respect to these parameters. The mathematical model provides effective guidance in design optimization. The performance predictions were found to correlate well with experimentally measured data. In an effort to explore the theory behind the Torsen differential design, the general subject of speed differentiation and torque bias generation is reviewed.

Conducting effective drivetrain NVH (Noise, Vibration and Harshness) troubleshooting is difficult because its execution requires commanding knowledge and experience on complicated vehicle system interactions. This is especially true for commercial vehicles due to the wide variety of available powertrain and chassis configurations and broad spectrum of vehicle applications. Furthermore, access to revenue producing commercial vehicles is often limited. Problem solving must be carried out within a tight schedule. Under these circumstances, a practical drivetrain NVH troubleshooting guide will come in handy. The objective of this paper is to document the “know-how” we have learned. Subjects covered in the discussions are underlying physics, problem diagnosis, solutions, and problem avoidance.