Mighty Max tranny problem

I can move the shifter through all the gears, but the tranny is locked up in a high gear when the engine is running even in the neutral position.
If I leave out on the clutch when it is running it acts like it is in fifth
gear no matter what the shifter position is. It will roll in neutral if the engine is not running. The only way to start it is with the clutch pushed in. It worked great then one day it just didn't act right, grinding and sticking then just went stupid on me.

have you tried taking your truck to the shop and having the clutch checked out a worn clutch could cause that or maybe a throw out bearing may be bad. have these 2 checked out