C6 shift question

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Dec 8, 2019 | 12:14 AM

dakotarider

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Tuned

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From: Pensacola, FL

C6 shift question

On my 75 F100 4x4 w/360, 33"tires 4" lift, (The Lone Ranger) I finally was able to get it back on the road today and it was not going into 3rd gear. I did a fluid service about 6 months ago. Does this sound like a plugged port issue or something with an adjustment? I have not adjusted anything external to the trans other than doing a basic service of fluids and filter. On the drive today, at 40 to 45 mph, it was doing good but wanted the 3rd gear so I didn't push the mph's any further. It did feel good driving it again though!

Dec 8, 2019 | 07:59 AM

caravaggio2000

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When does it shift into 2nd? I assume fluid levels are okay? Check your vacuum line to the trans and make sure it is leak free. Does the engine itself have good vacuum?

Dec 8, 2019 | 08:32 AM

F-250 WARHORSE

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From: starship enterprise

sounds like an issue in the vacuum modulator maybe bad, maybe not supplied with vacuum, look there.

Dec 8, 2019 | 11:37 AM

mikeo0o0o0

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From: Stanley, VA

Quote:

Originally Posted by F-250 WARHORSE

sounds like an issue in the vacuum modulator maybe bad, maybe not supplied with vacuum, look there.

X2 It sounds like the vacuum modulator, Check the line going to the modulator, make sure it's hooked up and the rubber hoses are in good shape. Look for holes, cracks or deterioration. If all that looks good, disconnect the hose at the modulator. If fluid leaks out, the modulator is bad. If it doesn't leak, the modulator could still be bad.

Dec 17, 2019 | 04:19 PM

dakotarider

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From: Pensacola, FL

Quote:

Originally Posted by mikeo0o0o0

Finally was able to go and look at the truck today. Started with the vacuum lines and then noticed the fluid was leaking from the modulator. Had to scrape a couple pounds of soaked South Dakota dirt and crud to get to the part! I went to the local Napa and they had three but they do not look like mine. Came home and looked all over the inner web and it is hard to find one that looks like this one. The part looks original but there are no markings other than some blue paint (which was one of the options at Napa). Looked up what the different color stripes designated but finding a part with the 2 vacuum lines is proving to be difficult. As far as I know, this is the original transmission in the truck. Both vacuum lines go back up the transmission and end up at the fire wall and then the rubber lines go to the port on my manifold.

Spot of fluid is from the top line.

Small spot of blue paint close to the center vacuum port. Notice the fluid in the port on the right?

Dec 17, 2019 | 05:02 PM

dlburch

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Joined: Jul 2005

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From: Kansas

https://www.macsautoparts.com/ford_t...tabs-container
https://www.rockauto.com/en/moreinfo...120127&jsn=475

Dec 17, 2019 | 05:17 PM

dakotarider

Thread Starter

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From: Pensacola, FL

Quote:

Originally Posted by dlburch

https://www.macsautoparts.com/ford_t...tabs-container
https://www.rockauto.com/en/moreinfo...120127&jsn=475

I was on the rockauto site when I seen your notification. Thanks, never heard of Macs. Does anyone know why some of these parts have 1 or 2 vacuum ports?

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Dec 17, 2019 | 05:41 PM

dakotarider

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From: Pensacola, FL

Quote:

Originally Posted by 5851a

Both hard lines run up the trans to the firewall and then the rubber vacuum lines go to the port on the back side of the intake manifold. Every corner I turn with this truck I find 1 more item that is a little different than other trucks of similar years!

Dec 17, 2019 | 10:31 PM

#10

F-250 WARHORSE

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From: starship enterprise

I believe it is not "uncommon" That is a vacuumport related to the egr. If you hook up the egr you will find on a cold drive before it warms up properly (it was -24 F where I went today) the vacuum port from trans isn't supplied correctly to the modulator and it isn't able to do proper shifts because of this. You would be able to get by with an ordinary modulator hooked to the manifold. If your egr isn't operable then the 2nd line probably means nothing anyway.

Dec 17, 2019 | 11:47 PM

#11

dakotarider

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From: Pensacola, FL

Quote:

Originally Posted by F-250 WARHORSE

Thanks WarHorse. I think I will go get the part at Napa tomorrow and just plug the extra port on the manifold that went to the second line on the modulator. I know that I will never get to -24 here in Pensacola Florida and if I move back to South Dakota, I will have to cross that frozen pond when I get to it!