The purpose of this paper is to share with the Product Engineering community relevant learnings on Internal Shift System for Manual Transmissions in order to promote transmission performance and eliminate potential concerns on shift quality and system durability for passenger cars. The subsystems in focus are the Manual Transmission Sliding Sleeve, Gear Fork, Rods and Synch Rings.
One important shift ability response that directly affects customer satisfaction is the Gear Clashing. This is a noise and vibration phenomena resultant of parallel synch activation while gear is intended to be engaged. This phenomenon was determinate by lack of Gear Fork design characteristics, which allowed two forks displacement at same time during cross-shifting maneuvers.
Through simulation analysis, which consists a detailed select and shift 3D stack-limit motion, an abnormal displacement of non-intended flyer fork displacement has been captured in a specific hardware under development. This failure can be also captured through a vehicle acquisition where pressure sound, case acceleration, shift displacement and shift effort oscillation determine a clear signature of phenomenon.
Solution consists on fork design changes in order to relief its interaction with shifter system during cross-shifting maneuvers.
This work intends to present the process of analysis, failure and final solution to prevent synch projects in the automotive industry.