while i was on the tractor using a tiller on 3 point hitch i heard a noise and now the pto will not work under load. i can engage it and it does turn but when i put a load on it, it quits turning. when the tractor is running, there is a rattle comming from what sounds like the front of the transmission. what could the problem be and is it going to require a tractor split?

More than likely the PTO drive tube in the clutch has lost its splines. This is a split to fix. Requiring both the drive and clutch PP to make it operate. Jim

Don't know if we call the front of transmission in the same place, but something else to check is the jaws and shift lever on the seasonal disconect if tractor is equiped with one. T shaped plate on bottom of center housing just in front of the transmission rear end housing. If the plate has a short lever with 2 bolt holes to change position the tractor came with one. You can also look in with plate removed to see if the pto shaft stops turning under load on toward front of tractor and go from there. Only problem is transmission oil will come out when plate is removed.

so what you are saying is that i can take a plate off the bottom and look at the pto side of the tranny to see where the fault is?

You can tell if the problem is there at the coupling or to front or rear of tractor. The PTO drive shaft is split under the plate. There's a solid coupling(more common on later 400) or the seasonal disconnect that has jaws that lock or unlock if shift lever is moved to disconect position. I didn't think about the diesel when I said see if the shaft stops turning under load. wouldn't want to try running it with oil drained down but a short time. If you could turn the pto shaft with pto in gear and engine stopped and get something to fail before the engine turns it would be easier to find. Could also remove the bottom front cover on center housing and listen for noise at the splines Jim N. posted about.
If problems in the pto drive train , some problems can be going toward engine from the disconect opening is the bolt getting loose that holds pto gear on the front lower shaft leading to failure. Bearing going bad on the shaft and letting gear drop. Gears failing or the splines that drive the top IPTO gear and shaft failing at the pressure plate. If the problem is just at the pressure plate and splines the tractor just has to be split at rear of engine to repair. Other things will require 2 splits unless the problems back at the pto. Another thing you can check with a helper before removing parts, but will have oil loss, is remove the drain plug in the bathtub shaped cover. second cover back on the bottom of center housing. Stick a stiff plastic tie in untill you feel the gear teeth hitting it and then see if it stops turning. Also the complete cover can be removed to observe the pto drive gears. Top cover on housing can also be removed also to observe gears. But if you can tell the problem is the drive splines at clutch by removing the dry compartment cover under the clutch, repair can be made without draining any transmission oil.

Ok. I appreciate all the help. Now I have a place to start. If the ipto has to come out, do I have to remove any of the drive train gears and shafts to get the ipto out?