The transmission modulator on a 1973 Ford LTD controls the throttle valve inside the transmission, using vacuum pressure from the intake manifold. A vacuum line runs from the manifold to the modulator, which is mounted on the transmission. Symptoms of a defective modulator include; hard shifting, late shifting and a rough idle with blue smoke from the exhaust. However, check your engine for vacuum leaks before replacing your modulator. A vacuum leak could cause the modulator to operate the throttle valve at the wrong time.
Instructions
- 1
Park your LTD on a flat, solid surface. Raise the front of the vehicle, using a floor jack. Place a jack stand under a solid piece of frame on both sides. Lower the frame onto the jack stands.
2Place a drain pan under the transmission modulator. Pull the vacuum hose off of the modulator. Remove the bolt from the modulator bracket, using a wrench. Pull the modulator out of the transmission.
3Put a light coat of transmission fluid over the O-ring on the replacement modulator. Push the modulator into the transmission. Set the hold down bracket in place and thread the bolt in to to hold it in place. Tighten the screw with a wrench. Install the vacuum hose on the modulator.
4Raise the vehicle off of the jack stands. Remove the jack stands. Lower the vehicle to the ground. Check the transmission fluid level and add as needed.
