The transmission vacuum modulator valve determines how much load is on the engine so the transmission can shift properly. It has a vacuum line that connects to the intake and measures the amount of vacuum in the engine.
In order to determine if whether transmission should shift, the modulator valve measures the load of the engine's vacuum. Engine load is the measurement of how hard an engine works at any given moment.
For example, coasting down hill will create a low engine load, while driving uphill with two passengers and a trunk full of luggage will create a high load. Thus, shift points for the transmission are figured according to the valve's measurement. The modulator valve is a part of the transmission vacuum. Inside the canister of the vacuum modulator, the valve works with a diaphragm and a calibrated spring to measure load.
When the diaphragm senses changes in engine vacuum because of load changes, the diaphragm pushes against the valve while the calibrated spring moves against the movement of the diaphragm. If the modulator valve is not working properly, the transmission will not shift properly. These problems can arise when the hose connecting the transmission to the engine vacuum cracks or burns, or collapses onto itself. This article was written by the It Still Works team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.
To submit your questions or ideas, or to simply learn more about It Still Works, contact us. Potential Problems If the modulator valve is not working properly, the transmission will not shift properly.
About the Author This article was written by the It Still Works team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.Posted on Jun 28, in Vehicle Transmission. It is important to know the signs of a bad transmission modulator valve as it can be hard to help it ones it is too late and you might have to go for a replacement. An adversely affected transmission modulator valve can cause some serious problems in your car.
Modulator valves come alive in function every time you shift gears of your car. Those who take changing gears for granted are not quite aware of how the modulator valve facilitates this for your vehicle.
Hence it is very important to take care of it as a modulator valve does one of the most important functions in the smooth working of your vehicle.
Vacuum modulator c4 tranny this one does not have a bracket?
The modulator valve function is to cater to the smooth functioning of shifting gears in your vehicle. It is, hence, necessary to be aware of the symptoms that point towards a bad transmission modulator valve.
Weaker and deteriorated engine performance is one of the primary symptoms of a badly functioning valve. Whenever any aspect of the engine performance of your vehicle deteriorates, it is suggested to take it seriously and cater to the needs of your transmission valve.
The primary function of your transmission valve is to facilitate smooth changing of gears of your vehicle, whenever you began to experience problems in shifting gears, it is one of the decisive symptoms of a bad transmission vacuum modulator. If the emission of nitrogen dioxide from your vehicle increases beyond a certain point, it is about time to give your transmission modulator a check and get it replaced if necessary.
The easiest symptom to recognize that your vacuum modulator valve on the transmission is all set to crash. The warning light on the dashboard should, hence, never be ignored in order to prevent serious problems in the functioning of your vehicle. The four symptoms mentioned above are all easy to recognize and one should waste no time in catering to the transmission valve once any of these symptoms are visible in the vehicle.
Getting the valve repaired or replaced in time can save your vehicle from experiencing severe damage in its functioning. Contact Me About.Gain extra benefits by becoming a Supporting Member Click here find out how! Send Private Topic View Profile. Greetings, I have a small vacuum hose coming from the transmission and I know it needs to go to the intake manifold but where? Also if this is not hooked up will it cause the transmission not to budge or having to put the pedal to the medal to slowly budge?
The carb I have is a Edelbrock and I have three ports in the font. The middle port is connected to the valve cover and the small one one the passenger side is hooked up to the distributor. I used the third one for the transmission but I will try to use the rear.
I just replaced the transmission filter, gasket and put 4 quarts in the tranny. Is that low? I don't think the original diameter or source of the vacuum supply is going to make any difference. I only have one car with a TH. Shifts fine. If you want to run your distributor off of full manifold vacuum like many of us do is an entirely separate discussion, if you want to run the tranny modulator off the same port just go to an auto parts store and buy a "tee" fitting, a short piece of hose to attach the port to the fitting, and plug both the distributor and tranny into the other ends of the fitting.
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Forum Rules. Thnx 64 Impala SS. The car will move however it wont shift automatically, it controls when the tranny shifts based on engine requirements. I'm not certain on this but, you might have control of shifts if you manually shift the gears. If not there is the port on the bottom backside of carb. Just be sure it is manifold vacuum or full vacuum. I don't have that hookup so I used a bolt to seal it off. I guess I'll hook it up there.
Can timing cause the tranny not to shift or vacuum?To shift properly, the automatic transmission has to know how hard the engine is working. There are two different ways that this is done. Some cars have a simple cable linkage connected to a throttle valve in the transmission.
The further the gas pedal is pressed, the more pressure is put on the throttle valve. Other cars use a vacuum modulator to apply pressure to the throttle valve. The modulator senses the manifold pressure, which increases when the engine is under a greater load.
The manual valve is what the shift lever hooks up to. Depending on which gear is selected, the manual valve feeds hydraulic circuits that inhibit certain gears. For instance, if the shift lever is in third gear, it feeds a circuit that prevents overdrive from engaging. Shift valves supply hydraulic pressure to the clutches and bands to engage each gear. The valve body of the transmission contains several shift valves.
The shift valve determines when to shift from one gear to the next. For instance, the 1 to 2 shift valve determines when to shift from first to second gear. The shift valve is pressurized with fluid from the governor on one side, and the throttle valve on the other. They are supplied with fluid by the pump, and they route that fluid to one of two circuits to control which gear the car runs in.
The shift valve will delay a shift if the car is accelerating quickly. If the car accelerates gently, the shift will occur at a lower speed. Let's discuss what happens when the car accelerates gently.
As car speed increases, the pressure from the governor builds. This forces the shift valve over until the first gear circuit is closed, and the second gear circuit opens. Since the car is accelerating at light throttle, the throttle valve does not apply much pressure against the shift valve.
4 Symptoms of a Bad Transmission Vacuum Modulator and Replacement Cost
When the car accelerates quickly, the throttle valve applies more pressure against the shift valve. This means that the pressure from the governor has to be higher and therefore the vehicle speed has to be faster before the shift valve moves over far enough to engage second gear. Each shift valve responds to a particular pressure range; so when the car is going faster, the 2-to-3 shift valve will take over, because the pressure from the governor is high enough to trigger that valve.
Gas-powered vs. Electric Cars: Which Is Faster? Are manual transmissions really faster than automatics? Prev NEXT. Automatic Transmissions: Valves and Modulators. Related Gas-powered vs.How do i remove it What part of the body of the modulator.
Is the bolt in front of it part of the modulator or is a seperatte piece They said this was easy but quite difficult at this point. Need more specific details on exactly how to remove it. What if yours is suppose to have a bracket holding it and the bracket is just missing?
If so you should be able to grab modulator and with a wiggle or two just pull it out of its resting place. Just a thought. These things are normally real easy to remove. From looking at pictures of the one for the c4 it should have a bracket. If you don't have a bracket it is probably just missing. Grab that thing and give it a tug and wiggle or two it should pop right out.
I think mines a screw on one? So pulling does not wrk unless it's screwed off. Any other suggestions. I have sent word to a friend who knows these trucks in and out. Hopefully he will be contacting you shortly. Sorry I could not be of more help. DavidH25 answered 7 years ago. Hi fellas. The C4 automatic has a vacuum modulator that senses change in the engine's vacuum due to throttle position and load changes.
With these changes the modulator adjusts the shift timing of the transmission according to the demand of the engine. Fabi: does yours look like this? They can be adjusted ya know.Just and update for those that pre-ordered Official Mustang T-Shirts! They are in print right now and should be dry and packed by the end of the week Anybody know what happened to the push in style c6 modulators from late on?
I had my C6 rebuild and the rebuilder installed a single vacuum port push-in modulator with a green stripe. Before the rebuild I had a dual vacuum port push-in type, I could not tell what color it was. Question: Where can I find information on what color strips mean? I have been told it has something to do with the pin size, but how do I tell if I have the correct one for my trans?
Also, which of the two vacuum lines does not get used with he single port version? Proud Space Junk Award Winner! There's a chart in the Ford shop manual that shows the desired shift points. If your transmission doesn't shift in the correct speed range you then change the modulator to achieve the correct shift point. I believe the vacuum diaphragm size also changes based on the color code. The longer pin raises the shift point.
Most replacement modulators are adjustable, which makes it easier and not as likely to have to buy a different modulator.
From what I've been able to gather, the black is for heavy duty use, with high shift points. The green striped ones seem to be a good choice for cars. You use the vacuum line that connects directly to the intake manifold for the single vacuum modulator. If you still have the emission controls EGR make sure the other line is removed and capped. You can post now and register later. If you have an account, sign in now to post with your account.
Paste as plain text instead.The modulator is held into the transmission with a stamped metal "fork" that is bolted into the transmission. Be careful during the removal because there is a short pin in the modulator that has to be replaced when you put the new one in.
On a Ford Aerostar : The automatic transmission modulator is on the passenger side of the transmission it might be behind a heat shield. The transmission modulator on a Ford Aerostar is on the passenger side of transmission behind catalytic converter. To remove you will need a 10mm socket with an extension long enough to reach over exaust pipe easiest way. On the Ford A4LD automatic transmission the modulator valve is on the passenger side of the transmission it might be behind a heat shield.
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All Rights Reserved. The material on this site can not be reproduced, distributed, transmitted, cached or otherwise used, except with prior written permission of Multiply. Ford Aerostar. Ford Aerostar XL. Ford Aerostar XLT. Top Answer. Wiki User Related Questions. Where is the transmission modulator for a 93 Ford Aerostar? Is the modulator on a ford aerostar accesible from inside the transmission?