I have a 86 MF240 and something is wrong with getting
PTO started. When the engine is running, if you try to put
PTO into high
RPM, the gear grinds and would not let you get into gear, but if you try to get it into low
RPM, you can get into gear no problem. Then when you turn the tractor off and try to put gear into High
RPM, it slip into gear no problem then you start the tractor and
PTO is running okay however the battery would need to be at full strength to make it work. If battery is weak then you won't be able to.
Any idea??

I am a bit worried!
And for your info,
PTO will run ok on high
RPM for as long as you run the tractor and will turn off when you pop the gear out.