1. Field of the Invention
This invention relates to controls associated with manual transmissions and, more specifically, to techniques to enhance the repeatability with which such controls may be installed on transmissions to provide reliable operation thereof.
2. Description of the Related Art
A manual transmission typically includes a range of gears which may be engaged to accomplish appropriate torque multiplication to provide propulsion of a vehicle. Additional gear ranges may be provided by use of auxiliary transmissions added in series with a primary manual transmission. An example of such an auxiliary transmission is a range transmission which includes a low and high range which provides twice as many gear ranges as are available on the primary transmission.
A primary transmission operated in conjunction with a range transmission must coordinate shift control therebetween. Such coordination typically includes a mechanical interlock feature which prevents a range shifter change from high to low or visa versa if the primary transmission is not in neutral position. The interlock feature is accomplished by use of an interface between the pneumatic valve typically and air spool valve that controls the position of the actuator cylinder of the range shifter and the mechanical linkage manipulated by the driver to select gear ranges. The interlock feature typically involves a pin which is translated from a neutral position to an in-gear position in response to any gear range selection. The pin includes a portion having a tapered end which engages detents formed in a shaft which translates in conjunction with the air spool valve which controls the operation of the range gear selection actuator. The air spool valve and detent shaft have an axis which is oriented orthogonal to the axis along which the pin translates. Establishing a proper aligned relationship between the valve body and the pin is critical to assure reliable operation. Conventionally, alignment of the valve body to the translating pin is accomplished by the alignment achieved via fasteners securing the valve body to the transmission. In such an implementation, the alignment achieved is a function of the tolerance stackup which may result in substantial misalignment of the respective components. Therefore, there is a need to accomplish alignment between the valve body and the transmission case which results in a reliable alignment of the translating pin with the interlock detents in the air spool valve.