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1967 400/400
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Thanks for the advice. From what you mentioned I bet the diaphragm is busted just from the sound it makes. I have one coming in next week and will give an update. It is an adjustable one so I’m glad you said to not adjust it haha
The general consensus is that the adjusting doesn't do a whole lot. My 67 is through 2nd gear, 20 feet off the line.
 

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Discussion Starter #22
Got the vacuum module on and it seems have help a bit but it’s still there. Should I try and lower the shift point so that when I let off the throttle it doesn’t come back down into second? It just needs to stay in third rather than coming out and going into second only then to turn right around and shift back into third.
 

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Got the vacuum module on and it seems have help a bit but it’s still there. Should I try and lower the shift point so that when I let off the throttle it doesn’t come back down into second? It just needs to stay in third rather than coming out and going into second only then to turn right around and shift back into third.
The issue is not likely the modulator. Have you verified your transmission kickdown is properly adjusted?
Letting off the throttle should cause the trans to freewheel.
If letting off the throttle always causes a downshift, then something is shifting it.
 

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Discussion Starter #24
The issue is not likely the modulator. Have you verified your transmission kickdown is properly adjusted?
Letting off the throttle should cause the trans to freewheel.
If letting off the throttle always causes a downshift, then something is shifting it.
Is the kickdown different from the downshift module on the pedal? Because if the kickdown is the bar connected to the neutral safety switch it’s not hooked up at all. I believe the previous owner broke or disconnected it and lost the parts.
 

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Is the kickdown different from the downshift module on the pedal? Because if the kickdown is the bar connected to the neutral safety switch it’s not hooked up at all. I believe the previous owner broke or disconnected it and lost the parts.
Yes, the passing gear kickdown on the TH400 is on the pedal. It works in conjunction with the solenoid on the transmission.
Something is causing your trans to downshift when it shouldn't. There are only so many things that can cause that.
Downshift solenoid is a very common one.
 

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Discussion Starter #26
Well I installed an aftermarket pedal since mine broke and I made the factory downshift solenoid bracket work with it. Maybe it’s too close but I really have to put it to the floor to make it actually downshift. Could the solenoid itself be bad? Is there a way to test it
 

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Yes, the solenoid could be bad. I posted about it in the begging of this thread. It's easy to test if it's working, however, with your condition, it sounds like it's working... even more than it should, which would mean that the wire harness had a short.that would cause it to activate. Check the harness between the pedal switch and the solenoid.

And, what were you saying about your gas pedal? You went aftermarket and rigged a switch?
 

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1967 400/400
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Does the original shift cable mount fit and clear with that pan? Did you have to tweak anything?

Bear
Everything was a direct swap, and they even include new bolts, a gasket, and a Delco Filter and extension tube. I couldnt be happier... Especially since the new pan flange is about 1/4" thick, so using no gasket at all and permatex ultra grey, I have no leaks! The whole job took less than an hour, and now it has more capacity, a heat sink, and a drain plug.
 

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Discussion Starter #30
Yes, the solenoid could be bad. I posted about it in the begging of this thread. It's easy to test if it's working, however, with your condition, it sounds like it's working... even more than it should, which would mean that the wire harness had a short.that would cause it to activate. Check the harness between the pedal switch and the solenoid.

And, what were you saying about your gas pedal? You went aftermarket and rigged a switch?
Yes I got an aftermarket adjustable pedal since mine broke. The kickdown switch mounts on its own bracket that used to work with the old pedal. I just drilled separate holes to mount the kickdown bracket and made it work with the new pedal.
 

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Yes I got an aftermarket adjustable pedal since mine broke. The kickdown switch mounts on its own bracket that used to work with the old pedal. I just drilled separate holes to mount the kickdown bracket and made it work with the new pedal.
Well it definitely sounds like your kicking down, when you shouldnt be. I would unplug the kickdown solenoid, on the drivers side, and then see if it still does it. That should quickly define this issue.
 

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I'm just wondering if the vacuum line is plugged into a ported instead of manifold source. It seems like that would create this type of issue.
 
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