You have an M5OD-R1 transmission in your 2001 Ranger
Doesn't read like a clutch issue
On the drivers side of the transmission there are 2 larger bolt heads, one at the bottom towards the rear(drain), one higher up and in the middle, the upper one is the Fill hole for adding ATF, yes automatic transmission fluid in a manual trans, no spelling mistake, lol
Remove this bolt and see if ATF drips out, it should if transmission is full.
If not add some.
BUT..... it may be time to change fluid as well, 15 years old now.
Ford Mercon V ATF is specified.
It takes just over 2 quarts so get 3 quarts.
Fluid in trans should be a nice reddish color, it starts going darker and blackish when its time for a change, stick your finger or a stick into the Fill hole and see what color the fluid is now.
You need a hand pump to get ATF into fill hole.
You can get units like these at autoparts stores: https://www.amazon.com/Plews-55001-L.../dp/B000BQW5LK