Yes I do hear a change in the engine. It sounds like something is turning in the engine, which is why I originally thought there may be some kind of sheer pin that would break if you hit a stump, etc. It sounds like the gear is turning but it is not connected to the shaft.
Depending on where the problem turns out to be, it's possible you can fix it yourself.
The M4030SU's pto is all mechanical - no solenoids, no hydraulics. The
M4030 has 2 hand levers for the pto. It has one lever for the clutch plate, and another is a pto shifter. A driveshaft runs from the clutch at the engine to a gearbox at the back end of the tractor. This gearbox reduces the rpm to pto speed, and also has a shifter to engage/disengage the pto. On some models the gearbox has 2-speeds, but on a
M4030 it is single-speed, with a neutral position.
First check the hand lever linkage for the clutch - maybe it's bent and keeping the clutch disengaged. Then check the linkage to the rear gearbox - make sure it is not bent or disconnected. There is shaft going into the box at the top left side, looking from the back, that moves the shifter inside. If necessary, disconnect the outside rod and exercise the lever with vise grips etc. Try turning the pto shaft by hand. Shifted one way it is free and should turn easily, shifted the other it will be connected to the pto driveshaft, clutch, etc. and should turn harder.
BTW, the indicator light switch is just on the linkage - it doesn't actually sense the engagement inside the rear gearbox. One other point, there are no shear pins etc. If the pto clutch and rear box are engaged and it still doesn't turn, then the problem is inside and more involved. Let us know what you find.
Pics are a rear pto gearbox for another model - the
M4030's box is very similar except it has an oil filler plug and a flat top.
