The Super661 MT-80A torque locking slider and  hardened hub assembly should be used when you have a Muncie 4 speed transmission that either has new gears that have torque locking engagament teeth or gears that have enough wear on those teeth that may cause a falling out of gear issue.  Typically very common example is letting off the throttle in 2nd gear and the transmission will slip out of gear. This is our own design which uses the slider and hub fits as the standard M-80A assembly. Improved slider design has a built it step to avoid the locking sliders from bumping up against the lower countergear. Designed by Paul Cangialosi.