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The uniqueness of heavy and medium duty vehicle powertrain design, compared to that of passenger cars, is two fold: vast variations exist from vehicle to vehicle because of mission requirements, and powertrain components are sourced from a diverse group of suppliers. Vehicle powertrain design involves selection of the appropriate major components, such as the engine, clutch, transmission, driveline, and axle. At this design stage the main focus is on power matching, to ensure that the vehicle's performance meets specifications of gradability, maximum speed, acceleration, fuel economy, and emissions[1, 2, 3, 4 and 5]. The general practice also demands that the durability of the drivetrain components for the intended vocation or application be verified. Equally important but often neglected in the design phase is the system's NVH (Noise Vibration and Harshness) performance, such as torsional vibration, U-joint excitation, and gear rattle.

It is well known that up-front FEA (finite element analysis) in product development will significantly reduce cycle time and improve product quality. The merit of using FEA in product design is evidenced by the mandate of its practice in the auto industry's QS9000 quality standard. Today, the usefulness of FEA in engineering product design is no longer an issue. Rather, the availability and cost for its extensive usage for product development is of concern. This is because until recently most FEA needed to be conducted by highly trained specialist. Recently, an alternative FEA implementation became feasible owing to the emergence of commercial software which takes advantage of several technological improvements such as P-element formulation and automatic mesh generation. As a result, some FEA jobs can now be conducted by less specialized engineers, offering the potential for fresh opportunities and challenges.

The uniqueness and challenge of heavy and medium duty vehicle manufacturing is that the vehicle&s subsystems and major components are procured from different suppliers. As a consequence, engineering task coordination for total vehicle performance optimization is required even if the intended design modification is only on one component. In the case of suspension design, related subsystems such as the drive axle, driveline, brake system, steering system, and engine mounts should all be included for review. The related potential problems for study fall into three categories, namely: function, durability, and NVH. The effective approach in addressing all these issues early in the design stage is through computer modeling and dynamic system simulation of the suspension system and related subsystems.

Although the methodology of straight bevel gear tooth form generation has been known for quite some time, few references are available in the literature. Presented in this paper are the general numerical procedures of spherical involute and octoid tooth form generations. We have proven that a tooth form generated from the latter approach, by simulating the rotation of a crown gear, matches exactly with the one from the former approach of unwraping a wire from a base circle. The advantage of using general numerical procedures rather than closed form equations is the flexibility of generating both standard and modified gear tooth profiles. In making the forging die, the gear tooth form must be developed with considerations of both the theoretical optimal geometry, and the dimensional compensation for heat treatment distortion.