C5 Auto Transmission Modulator
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Elder User
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From: Baltimore
C5 Auto Transmission Modulator
My 1973 F100 has a C5 automatic tranny in it. The transmission modulator has 2 vacuum ports on it and my question is "Why are there 2 ports?" This is the first time I have ever seen a modulator with more than one vacuum port. And, Ford switched back and forth between single and dual port modulators in the mid 70s. Does the 2nd port do something to minimize emissions? Can I use a single port modulator in place of the dual port modulator?
- ron
- ron
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The smaller port, farthest from the tranny, goes to spark vacumn. the larger port, nearest to the tranny, goes to manifold vacumn. Yes, you can use a single port modulator.
Unless you or someone changed it your tranny cannot be a C5, the C5 didn't come out till the 80's. If your tranny is stock it must be a C4. The modulator info is good for both trannys. You might also have a C6. Take a look here for help on tranny ID.
http://pages.prodigy.net/kennethl6/_wsn/page8.html
Unless you or someone changed it your tranny cannot be a C5, the C5 didn't come out till the 80's. If your tranny is stock it must be a C4. The modulator info is good for both trannys. You might also have a C6. Take a look here for help on tranny ID.
http://pages.prodigy.net/kennethl6/_wsn/page8.html
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Elder User
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From: Baltimore
It is definitely a C4. A guy in a tranny shop told me that it was a C5 and he said the clue was the fill tube which attaches to the right side of the transmission pan. Obviously he didn't know what he was talking about.
Do you have any idea what the purpose of the 2 port modulator is? I noticed in the Ford manual that the second port is referred to as the "EGR port".
Do you have any idea what the purpose of the 2 port modulator is? I noticed in the Ford manual that the second port is referred to as the "EGR port".
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I never have had a complete understanding why some models had dual port modulators. It probably had something to do with the early emission systems. A single port modulator will operate the transmission just as well as the dual port.
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