b7500 pto noises need help please

Hey guys I have a b7500d this is the gear driven transmission not the hydrostatic model. The other day I was tilling the garden and had been running the tractor for a hour. This unit has 800 hrs on it. Well any way the tractor never skips a beat but all the sudden it starts making a grinding/squeal noise. So I stopped when I pushed the clutch in the noise went away . I lifted the tiller and put the tractor in neutral. Let out the clutch and no noise so I shut off the pto and put the tractor in gear let out the clutch tractor moves fine no noise. I put the pto back on and put in gear let out the clutch no noise but when put the tiller down the noise started again. So it only makes noise when the pto is under a load. This tractor has a 540 and a 960 rpm pto just to see if it still did it in 960 I tried it no noise at all . Anyone got any ideas on where to start. I drained the fluid and checked for metal no chunks or shavings. I also checked the filter all looks good. I pulled the rear pto cover seal and looked over those gears and bearings all looked good. I also pulled the mid pto and looked up in there at all the gears I could see still all looks good. Thanks for any help guys

Not 1 to wait I decided to break her down. After stripping all the sheet metal seat and rops I took a peek into the rear end. All looked good in there but when I took off the front cover there she was I was missing a tooth on the 540 pto gear. Well next is the break it in half. Wish me luck

Here are a few . Got parts on the way

Gear cluster and be for I split it.