I have a JD 4240 powershift. It has shifted kind of hard into and out of 3rd for some time now. Recently began shifting hard in and out of 4th. Now, it's like the clutch doesn't do much in any gear. Tractor wants to keep moving when clutch is depressed. If I push the gearshift up through the gears with the clutch depressed, the tractor begins to move - nothing the brakes won't hold. When letting out on the clutch from a stop, there is a pause, and then it grabs pretty abruptly. Anybody have any hints before I take it to the shop?