tranny always downshifts

[Anonymous]

I just installed a 200ci and C3 tranny from a 80 mustang into my 60 Falcon. It is running well except the tranny always wants to downshift.

Upshifting is fine, nice and smooth from 1-2- to 3rd gear. But when I take my foot off the gas slightly it downshifts right away.

I am assuming this is due to the vacuum modulator. The vacuum modulator is responsible for the upshifting correct? And also the downshifting based on vacuum?

The vacuum modulator is connect to a vacuum port on my 1 barrel carb.

There is also a metal shift linkage that attaches to the transmission downshift lever and up to the carb throttle. But I thought that kicked in only when you increase throttle. I have played with adjusting that with no luck and currently have it disconnnected. The tranny still downshifts as described above.

I have a Haynes manual on Ford transmissions but it doesn't go over any of this info.

Any thoughts on how to make adjustments or correct this would be greatly appreciated.

 

[Mercury Mike]

Alright... I am going to give you the best information I have, but don't quote me, 'cause this is semi-unlikely (although it did happen to me)

The reason your tranny is kicking down constantly could be because the kickdown lever INSIDE of the transmission is broken. There's a threaded end on it, and the threads can crack, and stick it in kickdown position. Mine was really bad though, and wouldn't shift to third because of how much pressure it was releasing. I rebuilt my tranny and had to special order that part.

However! The vacuum modulator is supposed to plug into a port on the intake manifold, because it needs manifold vacuum to operate properly. I would switch those around first, and then once the modulator is on manifold vacuum see how it shifts. You can adjust the modulator's shift firmness, but first get it shifting right.

As for the kickdown cable and linkage from the throttle bar to the transmission, you set it by taking the spring off of the cable at the transmission, pulling the lever out as far as it will go (WOT on carb), and then adjusting the cable to be as far out as the lever will go. That is kickdown position. Hope this helps!

 

[Anonymous]

I just switched the vacuum modular connection from the tranny to a manifold vacuum port and that totally fixed it - no more downshifts.

Thanks tons! I wish they were all this easy to fix!

 

[Mercury Mike]

Well done! I wish I'd've been so lucky... =)