Date of Defense


First Advisor

Dr. Richard Hathaway

Second Advisor

Thomas Riley, Eaton Corporation

Third Advisor

Dr. Jerry Hamelink


A new range interlock design for a ten-speed, heavy-duty transmission has been developed upon the request of Eaton Corporation, Division of Truck Components. The function of this mechanism is to prevent the ability of the driver to change gears during a range shift. The range interlock executes this function by holding the three shifting rails in the neutral position as the piston in the rear transmission forces the range bar into the high or low range position. The new interlock system is completely mechanical. An interlocking shaft, similar to the three shifting rails, was designed and placed parallel to the rails. A connection was made between this shaft and the range bar, allowing the range stroke motion to be directly transmitted. As the interlocking shaft is in motion, it restrains the range slave actuating (RSA) shaft, thereby holding the three rails in place. Modifications to the existing RSA shaft were necessary to allow for the proper interaction with the interlock shaft. Some alterations of other parts were required, including adding new supports to the shift bar housing, modifying the range fork, and drilling a hole and allowing a coupler to move between the front and back transmissions. The components were designed for infinite life because up to 250,000 range changes may occur during the 500,000-mile guaranteed life of the transmission. Maximum normal and shear stresses were determined, and deflection and contact stresses were analyzed. It was assumed that similar processes have already been performed on the current parts that are relevant to the design. Because of time limitations, the parts could not be produced. It is recommended that in order to implement this design, further analysis be done in regards to the stresses and their effects on the parts that are already in use.

Access Setting

Honors Thesis-Campus Only