Check Balls and Separator Plates
The valve body separator and transfer plates are considered part of the valve body. They prevent flow in some passages while allowing flow into others. An automatic transmission contains many passages. Most are located in the valve body. The separator plate contains holes or orifices that form a seat for ball check valves. In time separator plates can become worn from these check balls. The holes in the plate become pounded out and distorted. The check ball can get wedged into the plate, enlarging the hole.
A valve body consists of different types of valves. Check valves are placed in hydraulic circuits to prevent flow in one direction while allowing flow in the other. When assembled, the separator plate contains the seat for ball check valves. The size of an orifice determines its flow rate. These check valves may or may not contain spring pressure to keep them in their seated positions. Make sure the check balls return to their exact locations.
The plate is accompanied by a gasket that forms a seal when assembled. When assembling and fastening the valve body to the transmission case, it's important to have the correct seal. An incorrect seal results in fluid pressure passing into the wrong hydraulic circuit and corrupting the transmission's shift timing.