F150 shifting problem

Hope someone can poi t me in the right direction. I have recently purchased a 1999 F150 with a v-6, standard fransmission (5 speed). Previous owner said he had just replaced the clutch. Here is the problem, after the truck has been running a while and after stopping the truck will not shift into gear. It does not grind orake any noise, it just won’t go into any gear. The only solution is to shut the engine off, place it in gear and retart the engine. During normal travel the transmission shifts up and down without any problems. The clutch does have a slave cylinder. Any suggestions? Thanks

My guess would be that the slave cylinder is failing when it gets heated up by radiated heat from the engine or exhaust system. If you verify that the hydraulics aren’t working when the engine is hot, I’d recommend changing both the master and slave units as a pair. If one is failing, the other is certain to follow.