C6 tranny issue

[Truetriplex]

I have a C6 coupled to a 428 and it does not down shift (passing gear) when I hit the throttle. What are some possible causes/symptoms and cures for this?

[Jac Mac]

Do you have a kick-down linkage/cable fitted?

[Snake2998]

Is the vacuum modulator connected to the inlet manifold and if so is the pipe not being sucked closed by vacuum?

[keezling]

Actually the vacuum modulator loss or no vacuum signal would cause maximum RPM upshifts in each gear regardless of throttle setting, kinda the opposite condition...

[breezridez]

Has the car been sitting for very long or is it driven regularly? It sounds like the governor may be stuck. usually from sitting for long periods in humid climates. I would try a couple of forced manual up shifts and down shifts. moderate to heavy throttle on the up shift. the forced downshifts will force the valve closed.

[Archrms]

Is this a new problem with an existing transmission that worked fine before, or is it a new transmission that you just installed?

[Truetriplex]

Thanks for all the input. I hope to find time this week to explore all the ideas suggested. To answer some questions, I just purchased the car. I immediately had the motor pulled for a freshen up, and to fix some small issues. I don't remember if the kick-down worked before and no, it had not been sitting. I wasn't around when it was reassembled so I will have to wait until I have time this week to really look at everything. Again, I do appreciate all the input. It has been a looooong time since I owned a Ford product and the memory is lacking

[Gaz64]

What carburetor do you have, and is the kickdown linkage connected?

You need to get it sorted, before you'll be pulling the trans out from failure.

Gary