Hi My 1966 Toronado doesn’t upshift till about 55 mph normal driving and when floored it doesn’t downshift
i can make it up shift and downshift manually
Any ideas?
Thanks
Randy

 

Have you checked to see if your automatic transmission modulator line is attached to the transmission valve and a good vacuum source?

 

I will check that in the AM
thanks

 

No cracks in the rubber vacuum hoses which attach to the metal line (might need to replace with new), no transmission oil leaking from the valve at transmission (valve may need replacement).

 

valve at transmission meaning modulator?

 

Yes. Modulator valve is installed in transmission which is where line attaches.

 

I’ll check
thanks

 

Verify that your kickdown switch isn't shorted. Pull the plug from the switch or trans (whichever is easier to reach) and see if it upshifts. If not, the problem is likely the vacuum modulator or the vacuum signal to the modulator. You can temporarily tee a vacuum gauge into the line that runs to the vac modulator at the trans and see what vacuum readings look like.

 

Is it possible that his kickdown solenoid is stuck open (electrically good but physically stuck)? So it would be in "kickdown" mode always?

 

Which is why I suggested disconnecting the plug in post #8 above. FYI, the kickdown solenoid valve is normally open. When voltage is applied it closes to engage the kickdown.

 

You 100% on that? I could have sworn I read in the CSM that the kickdown on the TH425 is a normally closed, powered open switch.

 

This video shows what I mean:
TH400, I know, but similar. You can see how the valve is normally held closed and powered open @ the 1:15 mark. Unless I'm completely misunderstanding.......which is entirely possible.

 

You are correct. My apologies. I swear I read it as normally open, but the CSM clearly shows that it is not. Thanks for catching that.

 

Finally! I got one over on Joe! I believe this calls for a celebration.