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C4 trans vacuum

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C4 Modulator vacuum question. My C4 transmission builder said he didn't think he could change the particular type modulator out to soften the shift from first to second but said I could unplug I think the front vacuum line and put a screw it the line and it would soften it some.

Anybody know about this? I recall him saying something about a double vacuum or something with that modulator. Sorry for the stupidity and poor info but I know nothing about transmissions. I would look at a few things. Behind the modulator is a pin. Stock is 1. You may have a longer pin. Then a different modulators.

They have colored strips on them. Also the modulator should have a lil adjustment screw inside where the vac line connects. That can be turned to adjust shift points also. Make sure your kick down is hooked up.

Does your bronco have its vacuum can mounted on the firewall behind the throttle lever mounted on the firewall?.

It may soften and delay the shift a little. A day worth getting up for is a day worth learning something new. Your '74 may have 2 vacuum nipples, explaining the "double vacuum" reference.

c4 transmission vacuum line diagram

Some '73 and '74 C4s used this in conjunction with the EGR. Ford figured out this wasn't one of their better ideas, and dropped it, in late ' I would just get a yellow stripe single nipple modulator and use one of the vacuum lines to connect it directly to the vacuum tree in the intake.

These modulators are adjustable by turning the slotted screw in the nipple. Also ask your transmission builder if he installed a shift kit. That would also explain the hard shifts.

Some of them put shift kits in every job. The Bronco C4 never needed a shift kit. I had the same problem and had to scour the junk yards for an unmolested C4 valve body, to fix it.Due to shipper and supplier delays, your order may take longer to arrive. Display Options. Already know the part number you need? Click here to enter them directly into your cart. If you are an international customer who ships to a US address choose "United States delivery" and we will estimate your ship dates accordingly.

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How to Find and Fix A Vacuum Leak

Loading, Please Wait Sold individually. I am in the United States. International Customer Options. Delivery Options If you are an international customer who ships to a US address choose "United States delivery" and we will estimate your ship dates accordingly. International delivery. United States delivery. Automatic Transmission Vacuum Lines Replace your rusted or worn automatic transmission vacuum lines with something better.

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Recently Searched. Show Recent Vehicles. X Welcome International Customers! Results 1 - 25 of View By Product Groups. Large Image. Instructions Large Image.You probably see automatic transmissions as a convoluted maze of gears, clutches, bands, and complicated hydraulics.

However, it may surprise you to know that most automatic transmissions work via a very simple principle known as hydromechanics—planetary gear sets, multi-disc clutch packs, bands and drums, and a hydraulic control system. Most transmission builders agree that Ford's C4, C6, and FMX transmissions are not only rugged and dependable, they're also simple to identify, rebuild, and service. Our goal here isn't to show you how to rebuild these vintage Ford automatics.

Instead, we want to provide you with information about how to identify them and understand how they work. Because the C4 and C6 were developed at the same time, they're very similar; the only real differences are size and low-reverse function. The C4 has a low-reverse band as does the FMX.

c4 transmission vacuum line diagram

The C6 has low-reverse clutches instead of a band and drum. As owners of ''66 automatic Mustangs can attest, the shifter had a large "green dot" indicator in the second position for normal shifts, along with a smaller dot indicator in the first position for starting out in second gear on snow and ice.

This is the way the C4 remained until production ended in At that point, Ford began production of the C5 Select-Shift, which was little more than a C4 with locking torque converter and revised hydraulics for fuel efficiency. Because the C5 has a wider bellhousing to accommodate a locking torque converter, it will not fit in the tunnel of your classic Mustang.

Understand Automatic Transmissions, Mustang C4, C6, and FMX

Over the years, there were important changes to the C4. From ''69, the only change of note was the ''66 "Dual Range" valve body, which is different than '' If you want to upgrade your Dual Range C4 to the conventional ''69 pattern, all you have to do is swap the valve body.

For '70, Ford changed the C4's main case and valve body to an eight-bolt pattern.

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Ford introduced the C6 for '66 to replace the outdated Borg-Warner MX cast-iron transmission, which was never available in the Mustang. An all-new design, the lightweight C6 employed a lot of the same features as the C4. The C6 remained in production through '96 because it was used in a variety of non-car and truck applications.

To improve a C6's durability, go with a wider intermediate band and "R" servo Cobra Jet for a more solid hook-up during upshift. Outside of the intermediate band issues just mentioned, the C6 was engineered for durability from the get-go. It is a fiercely dependable transmission.


Don't make the mistake of picking up a "Dual Range" valve body for your C6. Shifter detent is another issue to watch for. Does your C6 have a valve body detent or transmission case detent? And finally, is your throttle valve vacuum modulator screw-in before '72 or press-in 'up? From ''69, C4 transmissions had a. In '70 only, Ford went to a. Another change came in '71 with a. The FMX is a standalone cast-iron three-speed automatic that was in production in various forms beginning in When Ford introduced the C6 in '66, these old ironsides were dropped in favor of the newer, lighter C4 and C6 transmissions.

When C4 and C6 production shortfalls created challenges in the late s, Ford turned to the tried and proven FMX with beefy MX internals inside the smaller FX case for the engines that arrived in ' It was a rugged and dependable three-speed automatic. The Ravineaux planetary design consisted of fore and aft planetary gear sets in a single package, which is what makes it different than the separate Simpson planetaries used in the C4 and C6.

Aside from this difference, the FMX operates much the same way as a C4. Band adjustment is similar, with a setscrew and locknut like C4 and C6. FMX intermediate and low-reverse servos are located inside the case.Forums New posts Search forums. Media New media Search media. Resources Latest reviews Search resources. Log in. Search Everywhere Threads This forum This thread. Search titles only. Search Advanced search….

Everywhere Threads This forum This thread. Search Advanced…. New posts. Search forums. C4 Auto Vacuum Line. Thread starter pyroman Start date Sep 26, JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.

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Founding Member. Jul 28, 3 18 34 Ennis, Texas Visit site. I've got a vacuum line at the back of the engine running along the bell housing.

I read somewhere that this line was important to make sure the transmission is shifting properly. I can't remember where I got this info, I spent all morning flipping through my shop manual trying to find out about it but failed. What I need to know is where it hooks up. JC Mustang Founding Member. Nov 1, 0 0 Layton, UT. There should be a "vacuum tree" screwed into the back of your intake manifold to which this connects.Welcome to the ClassicBroncos. To take advantage of all the forum features please take a moment to register.

Registration is fast, simple and absolutely free so please, join our community today! If you have any problems with the registration process or your account login, please contact contact the admin. If you've lost your password click here. C4 Vacuum Modulator Hook-Up. My Bronco is running a C4 transmission, the vacuum modulator has two ports, one is a little bigger than the other. What hooks up to these ports? I know one get's intake vacuum but what is the second port for?

Ported vacuum? Can I swap it out for a single port modulator? Thanks once again This can in most cases be replaced with the green stripe version and get better results for the shift characteristics.

The red-stripe dual diaphragm equipped C-4s use a different modulator retaining clip. This retaining clip is held in place by an extension housing bolt that is located just above the modulator. When changing the modulator to a single diaphragm type, you need to get the correct retainer from the dealer or the boneyard. C-5s also use the same C-4 retainer made for the single diaphragm modulator.

The dual diaphragm retainer will cover access to the hose connection on the single diaphragm modulator. The retainers are made of spring steel. Usually found on larger engines with strong vacuum signals, and trucks with earlier governor shift point calibration.JavaScript seems to be disabled in your browser. You must have JavaScript enabled in your browser to utilize the functionality of this website.

Literally millions of Ford cars and trucks were equipped with C4 and C6 automatic transmissions between the introduction of the C4 in and the replacement of the C6 in the s. These purely mechanical no electronic controls automatic transmissions are still popular with racers, hot rodders, and restorers today due to their simplicity and low cost.

Cores can be purchased and rebuilt to suit the needs of a specific vehicle for much less than a comparably rebuilt modern overdrive automatic transmission with electronic controls.

But, they lack the overdriven gears and lockup torque converters the newer transmissions rely upon to boost fuel economy figures. Ford had a fundamental challenge to its direction and future in the late s—how to shed a stodgy image and dated technology. This effort began with a new generation of skirted-block FE-series V-8 engines in InFord introduced its lightweight-iron Falcon and Comet sixes.

The degree Fairlane small-block V-8s followed in The MX was a large-case automatic and the FX was small. Although these transmissions were rugged and dependable, they were heavy, complex, and not easily adapted to performance applications.

This is when Ford engineers developed lightweight aluminum-case automatic transmissions for an exciting lineup of automobiles that arrived in the s. When Ford Falcon and Mercury Comet were introduced forthey were available with a new lightweight Ford-O-Matic 2-speed transmission.

It was designed and manufactured by BorgWarner for new-generation gray-wall-iron straight-6 and small V-8s. What made the little Ford-O-Matic different than its predecessors was its aluminum case and steel hard parts inside and out. In early applications, the Ford-O-Matic transferred heat to the atmosphere via the torque converter and cooling vents in the bellhousing, instead of using fluid as coolant and a transmission cooler in the radiator.

Later versions had a transmission fluid cooler in the radiator. The Ford-O-Matic and Merc-O-Matic were available behind the, and ci straight-6 engines, along with the and ci V-8s, which came later in Bellhousing and main case were cast as one to reduce weight and reduce the likelihood of leakage.

At first glance, the 2-speed automatic looks like a cast aluminum FX or MX case. Ford took what it learned from the 2-speed BorgWarner automatic and applied it to the C4 3-speed Cruise-O-Matic that arrived for the model year.

The C4 employed a new state-of-the-art Simpson compound planetary gear set, which became an industry standard in the years to follow. The 3-speed C4 Cruise-O-Matic was introduced just in time for the model year.A lot of people take gear shifts in their vehicle for granted.

c4 transmission vacuum line diagram

But every time your automatic transmission needs to shift into a different gear, there is a vacuum modulator inside which ensures that the gear shift can be accomplished. The vacuum modular is a load sensor inside of the engine which calculates how much of a load is being placed on the engine of your car. Once it detects this amount, it can allow the transmission to shift appropriately.

Older model vehicles used to have cables connected to the throttle valve to accomplish this task. Either way, both technologies have the same function. When we talk about the load on the engine, we are referring to how hard it must work just to maintain its functionality. The load is obviously referring to the weight and pressure placed on the engine as it continues to move the vehicle.

For example, when you drive your car downhill, there is a smaller load on the engine because gravity is helping the vehicle move. The vacuum modulator measures the amount of this load so that the engine knows how hard to work to sustain the demand being placed on it. Most modern vehicles have a vacuum modulator in them.

If your vacuum modulator were to become defective, there are certain symptoms you could recognize right away to determine this. Here are four of the most common symptoms of a malfunctioning vacuum modulator. The main symptom you will notice is poor engine performance.

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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.

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This will ultimately affect the fuel economy and efficiency of your vehicle. Another easily noticeable symptom of a bad vacuum modulator is having the check engine light illuminate on your dashboard. The computer of your car will know right away when the modulator sends a bad signal, which will cause the warning light to come on.

However, there are many reasons why the engine warning light can come on besides this reason. So, do not automatically assume it is a bad vacuum modulator unless you are experiencing at least a couple other symptoms as well. If you have excessive amounts of nitrogen dioxide emissions coming out of your vehicle, this may indicate that the vacuum modulator is no longer able to properly regulate these emissions.

Most people find this out when they have an emissions test done on their car, which is required by some states. As you just learned, the vacuum modulator is what allows the transmission to shift properly.