One of the most challenging shift complaints to diagnose is a harsh shift. The most likely cause is a check valve seal in the valve body. These valves are actuated by fluid pressure and seal against the passages with o-rings. The movement of these valves can become “sticky” due to seal leaks and varnish in the passages. This hesitation can cause shifts that can be delayed or suddenly engage. This video will focus on the additives and conditioners that can rejuvenate the seals and eliminate varnish in the passages of the valve body.