Will using the 3 pt hitch when setting still make it stall..?? This I could see being a hydraulic issue, but not for long. I'm thinking if it's building enough pressure to stall the tractor, it would take out the front seal on the pump, and put your hyd. oil in the crankcase. Pulled the dipstick on the engine lately..??
Or just using the 3 pt. hitch when in third gear make it stall?
If it starts on it's own from the get go, I can't really see it being an alternator problem. Something mechanical seem to be dragging it down.
Have you had the tractor long, or just get it. Reason I ask... Did it just start this, or was it like this, if you just got it. If you just got it, did you check the hyd. & trans fluids..??
Also wondering what the brakes are like on it. It almost sounds more like a brake issue with them dragging, and pulling the tractor down. If the braking ability to stop is poor, then something is wrong. Those twin disc brakes will stop in in a heartbeat if working properly. If the tractor has ever set out a lot, could be all full of rust and crap, have the brakes half set, and pulling it down. In 1rst and 2nd, it maybe has enough power to overcome the braking. There are 3, 7/8" ball bearings in the brake expander. That can get all rusty, and the ball bearings crudded up, and not work properly. There's only like 4-5 bolt to take out, and the whole unit comes off for easy service. Also if the return springs are rusted and broken, it will not allow the brakes to come back to the full release position.
If it were like a bearing on the mainshaft of the trans, I'd think by now you'd hear some sort of noise coming from that area.
I have a 240 Utility, but with Fast Hitch. Never had an issue like that, but the brakes do get a little grabby after going through the spring sweat we get here in Ohio, and the expanders must get a bit of rust on them.
Will the tractor coast if on an incline, hill etc., very easily, if in neutral, or just the clutch disengaged? It should...
Hard to diagnose over the internet with limited understanding of what's going on. But just for kicks, I'd pull the brake housings, and check inside. As mentioned, 4-5 bolts hold them on, and remove the adjusting nut. Maybe some persuasion with a rubber mallet, and it should come right off.