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In a transmission for Automobiles, the driver's comfort of smooth shifting and selection of gears is a major concern for the transmission designer. To achieve this comfort, lot of work and improvement has been done in the past few years and still some more improvements are in continuation by the automobile manufacturer. Apart from the smooth shifting and selection of gears while driving, the safety of the driver is also a major concern for the vehicle manufacturer. This paper relates to a safety Interlock mechanism of vehicle gear shifter selector lever to a drive position, until a predetermined condition is satisfied. There are various gear shift pattern exists in the vehicles, which depends upon the number of gears in the gearbox. Generally, two types of gear shift pattern are commonly used in commercial vehicles. 1st-2nd, 3rd- 4th, 5th-6th, Rev and Rev-1st, 2nd-3rd, 4th-5th, 6th.

Tolerance stack up is one of the most important exercises of design team to ensure the interchangeability of the components and the sub assemblies in the product having a large product family. Optimized allocation of tolerances between the components in a product helps to reduce the conflicts between the designer and the manufacturer. Automotive gearbox is one of the most important and critical aggregate of any vehicle in which the assembly of gear train performs the function as required. In the gear train, numbers of gears are meshed with each other and transfer the torque on wheels as per the required performance of the vehicle. When the gears are meshed and rotates some noise would generate because of the rolling and sliding action of the gears. This noise is known as “whine noise”. Now days this whine noise is increasingly becoming an important subject for the transmission designers. Gear whine is a total noise that is noticeable to passengers and makes them uncomfortable.

Gear design is one of the most critical components in the Mechanical Power Transmission industry. Among all the gear design parameters pressure angle is the most critical parameter, which mainly affects the load carrying capacity of the gear. Generally gears are designed with a symmetric pressure angle for drive and coast side. It means that both flank side of gear are able to have same load carrying capacity. In some applications, such as in wind turbines, the gears experience only uni-directional loading. In such cases, the geometry of the drive side need not be symmetric to the coast side. This allows for the design of gears with asymmetric teeth. Therefore new gear designs are needed because of the increasing performance requirements, such as high load capacity, high endurance, long life, and high speed. These gears provide flexibility to designers due to their non-standard design.

Manual transmissions, dual clutch transmissions and automatic manual transmissions use a synchronizer mechanism to have smooth gear shifting inside the gearbox and good shift feel inside the driver's cabin. Smooth gear shifting is related to the time required to complete the synchronization process inside the gearbox and a good shift feel related to the force required to shift the gear inside the driver's cabin. Moreover, good shift feel depends on efficiency of gear shifter mechanism, driveline vibrations and double bumps. Transmission gear shifting performance is the major concern area for all automotive and commercial sectors of vehicles. Transmission gear shifting performance in synchromesh gearbox depends on the capacity of synchronizer to produce sufficient frictional torque in required synchronization time and shifting force on the lever.

In today's automotive industry Benchmarking plays a vital role to improve performance, quality of critical functions and key areas of an organization by understanding and evaluating the products & processes in relation to Best Practices. Gear Reverse Engineering (here in after called as GRE) a part of Benchmarking is an activity which follows an analytical approach to calculate basic key parameters for an unknown gear pair. This paper propose a diagnostic tool/method, which determines basic gear parameters for an unknown gear pair, by simply measuring few dimensions as input followed by step wise analytical approach. This tool/method simplifies the gear designer job at initial stage by eliminating frequent trial & errors, iterations and complex measurements, which saves time & cost.

In automotive Transmission especially in Manual shift Transmission, a mechanism is provided for smooth and quick shifting of gears known as Synchronizer. A synchronizer mechanism having a Sliding shift sleeve, synchronizer ring, clutch body and clutch body ring as the main components to shift the gears smoothly. A synchronizer ring and Clutch body ring having outer tooth with inclined faces i.e. chamfer on their end facing towards gear shift sleeve, having inclination faces to mesh with the same inclined faces of blocker ring and clutch body ring for smooth shifting with less effort. Generally in cold environment certain forces are acting inside the Transmission to reduce the speed of rotating elements, these force are called drag forces. Mostly these drag force are generated due to high viscosity of transmission oil and large Inertia of masses of rotating elements, bearings and oil seals friction etc..