I have a '65 F100 w/302 and FMX transmission. This weekend it decided to stop downshifting. The first time you start it for the day it will shift thru all three gears but when you come to the first stop it doesn't downshift. You can do it manually but not on it's own. If you are cruisin' and floor it the thing will down shift and boogie but once again when you come to a stop it doesn't downshift.
It stays in 3rd gear when you go to take off again. If I stop and put it in neutral, then reverse, neutral then back in drive it will once again take off in first and shift thru all three gears.
Any help or advice would be greatly appreciated!

 

The governor is hanging up.
Remove the extension housing.
The body is held in place with 2 screws.
Clean the valve real good.
There is a small spring that can be added to prevent this.
Pay attention to the position of the body.
If you get it bassackwards it wont shift.

 

Someone else thought that my govenor was sticky and suggested putting it in reverse and flooring it. I did this three times and now everything is working fine. If it does start sticking again I'll clean the valve as you said to do.
Thanks for the help.