This PDV 9104 is a simple control valve that will give the vacuum modulator on the transmission the correct vacuum signal from beneath the blower until there is boost.
This means that the transmission will receive a true engine vacuum signal that is required for proper shifting.
As soon as the valve senses boost beneath the blower, it switches the valve to show zero vacuum for the transmission modulator.
Zero vacuum tells the transmission there is load, wide open throttle condition and the transmission will increase line pressure to minimize the amount of slippage.
Without this valve the trans modulator would see boost instead of vacuum if connected below the blower and too much vacuum if connected above the blower causing radical shifting and or excessive slippage which could burn up the transmission.
The top line hooks up to vacuum port above the blower (NOT PORTED VACUUM) The fitting sizes are 3/16 and 1/4.
