The original design of Ford 5R110W valve body included five hydraulic pressure switches. Although these switches were never actually enabled by the OEM or monitored by the computer, early valve bodies came through with all five switches installed as dummy plugs to seal up their circuits. Later valve bodies have all pressure switches except the direct clutch pressure switch removed, and the locations in the casting were left unbored to essentially seal the circuit. The remaining OE direct clutch pressure switch in the late valve bodies is still not enabled or computer monitored.
With the excessive high line pressure that is a frequent problem in these units, it is common to find the OE pressure switches/dummy plugs damaged. This can result in loss of shift solenoid control pressure and shift complaints. Unused and damaged switches/plugs can be replaced with Sonnax pressure switch O-ringed end plug kit 36940-17K to prevent future damage and oil loss. The O-ring provides positive seal to prevent loss of shift control pressure