Table of Contents
Where is the modulator valve located?
The modulator valve is attached to the intake manifold with a vacuum line.
Where is the transmission vacuum modulator located?
The vacuum modulator is on the passenger side of the truck on the rear of the transmission just forward of the tail shaft cover. Pull the hose off and lay it aside. When the hose is removed, look for transmission fluid in the hose. Shake the end of the hose and see if any transmission fluid comes out.
What are the symptoms of a bad transmission modulator?
When you have a bad modulator valve, some or all of the following symptoms will begin to manifest themselves:
- A whistling sound (from a leaking diaphragm)
- White smoke coming out of the exhaust (from a leaking diaphragm)
- Early or late shifting.
- Hard shifts (usually causing the car to jerk)
- A rough idle.
What happens when a vacuum modulator goes bad?
The main symptom you will notice is weak engine performance. If the diaphragm of the vacuum modulator were to have a leak in it, you will have a leaky vacuum and your EGR system will shut off. If the vacuum leak is too severe, then you will notice less power in your engine as well as acceleration problems.
How do you adjust a modulator valve?
Remove the vacuum line from the end of the vacuum modulator. Use a small slotted screwdriver to turn the adjuster that is located inside of the vacuum fitting. Turn the adjuster clockwise for earlier shifts and counterclockwise for later shifts. Make small adjustments of 1/8 to 1/4 turn at a time.
How do you test a modulator?
Testing the Modulator
- Block the rear wheels.
- Locate the vacuum modulator on the passenger side rear of the transmission.
- Pull the vacuum hose off the modulator and install the vacuum pump.
- Look for any transmission fluid running out of the vacuum port on the modulator, indicating a broken diaphragm.
How do you remove a modulator valve?
Unfasten the bolts holding the modulator valve onto the transmission. Remove the modulator valve by twisting it counterclockwise. Pay attention to the actuating rod, which might fall out in the process. Place the actuating rod inside the new modulator valve and then insert the new valve into the receptacle hole.
Can you adjust vacuum modulator?
Most factory vacuum modulators are sealed and cannot be adjusted. Some early Ford and GM vacuum modulators are adjustable and adjustable modulators are available from aftermarket suppliers. An adjustable modulator will allow you to make the transmission shift a little bit earlier or later.
What does a vacuum modulator do?
Vacuum Modulator is an engine load sensing device that converts engine vacuum into a transmission valve body input. As the throttle blades are open the manifold or engine vacuum drops as ported vacuum (above throttle blades) increases.