The gear selector is one of those parts of a K-Series transmission that can easily be overlooked during regular maintenance. Over time, the internal components wear against each other, increasing clearances and eventually pushing the assembly outside of its original specifications. As that wear progresses, you may begin to notice loose, vague, or inconsistent gear changes—problems that even upgraded shifter cables or a high-quality shifter can’t completely solve. In this article, we’ll tear down and rebuild a worn K20A/A2/Z1 6-speed gear selector, inspect the components for wear, replace what’s needed, and bring the assembly back into spec before installing it in our race car.
Consider upgrading the gear selector springs now:
Replacement OEM Breather cap:
Replacement K20A/A2/Z1 6-Speed Selector Interlock
Replacement Spring Perch
Replacement Spring Washer
Replacement Selector Shift Arm 
Replacement Shift Arm Bolt
Replacement K20A/A2/Z1 Mainshaft Brake Arm