Firstly check that the selector linkage is correctly adjusted and is working as it should.
Then check the fluid level as follows:
With the transmission at normal working temperature, the engine idling, and the car on level ground, run through the entire selector range allowing a few seconds in each position to allow it to engage, starting and finishing in PARK, then, with the engine still running walk round remove and wipe clean the dipstick and re-insert to take a level. You will have time for a few quick dips to try and get an accurate level. If you add fluid repeat the whole procedure before taking another level. Use only ATF-G or fluid that meets Ford spec. M2C-33G. DON'T use any of the DEXRON type fluids. A small amount of white blackboard chalk rubbed on the bottom of the dipstick, and then wiped off, dries it and makes seeing the level easier.
The fluid should be red and clean, not brown and burnt.
Check the condition of the throttle bracket bush if fitted.
Check the condition and adjustment of the kickdown cable.
Then check the fluid level as follows:
With the transmission at normal working temperature, the engine idling, and the car on level ground, run through the entire selector range allowing a few seconds in each position to allow it to engage, starting and finishing in PARK, then, with the engine still running walk round remove and wipe clean the dipstick and re-insert to take a level. You will have time for a few quick dips to try and get an accurate level. If you add fluid repeat the whole procedure before taking another level. Use only ATF-G or fluid that meets Ford spec. M2C-33G. DON'T use any of the DEXRON type fluids. A small amount of white blackboard chalk rubbed on the bottom of the dipstick, and then wiped off, dries it and makes seeing the level easier.
The fluid should be red and clean, not brown and burnt.
Check the condition of the throttle bracket bush if fitted.
Check the condition and adjustment of the kickdown cable.