JD 520 PTO problems

I have a JD 520 with PTO problems. For years the PTO would "hammer" when in use & the tractor turning right or left. Finely the other day the PTO stopped turning & it makes a grinding sound like the gears are not meshing. My questions are: did a bearing go out & a shaft moved so the gears don't mesh? Can this be repaired from the top or do I have to split the tractor? Anybody have any suggestions or advice? Thanks much--You ALL have been very knowledgeable & helpful in the past.

If the PTO problem is in the PTO clutch and output geartrain area it can be serviced from that (back) area, by removing the casting the shaft exits from, without ANY teardown of the rest of the tractor.

If it's farther ahead in the geartrain from the RH side of the crankshaft though the bevel gears in the belly of the tractor there can be a LOT of teardown needed to get to the problem!

Suggest posting lower down on the page in the DEERE-specific Forum, as well.

Below is a link to the parts catalog (in .pdf format) at the official John Deere parts site, which shows parts breakdowns of the various parts of the PTO system.
520 parts

It is normal for them to make a racket when turning,, the angle of the you joint makes this happen,,seems worse on a 2 cylinder..

The hammering when turning may have been directly attributed to the geometry of the front universal joint's relationship to the
hitch pin location, the phase relationship of the yolks in the PTO shaft, and angle of the turn.
1]If the Ujoint location (front to back) is at or close to the hitch pin, the front joint is angled much more, or has all the
angle compared to the rear joint in that shaft. This causes rotational accelerations and decelerations in the the shaft that are
not cancelled by the rear joint. If not canceled, the change in RPM 4 times per rotation (faster slower faster slower) is trying
to change the speed of the driven attachment, be it a mower, or baler. The inertia of the implement causes this to be a radical
vibration. The hitch point pivot needs to be rearward of the front joint So that the angle in a turn is far more equal between
the two joints.
2} If the two Ujoints are not in phase (on a piece of paper draw a backward capital C draw a line from this wrong facing C about
an inch long and draw a correct facing capital C. The yolks of the shaft must be oriented the same way as these "C"s. That is
they must be coplaner. If they ar not, the shaft will vibrate and make noticeable vibration at nearly any angle. Each joint
accelerates out of phase with the other accentuating the issue.
3} All simple Ujoints create the acceleration deceleration issue. The shaft between them is supposed to be the only thing that
is subject to this velocity change if the angle is greater than about 25 to 30 degrees per joint the vibration will shake things
apart.
I am not aware of the construction of the JD PTO drive, so others will need to fill this in, but the Knocking caused it. Jim

Hope these pictures are of assistance:

Bob. Owner JD 520 and other Coloured tractors:

UPDATE-- If I throw the shifter lever out of gear, no grinding, which makes me think it might be something to do with bearing item #30 (JD 8561). It doesn't seem
to mater if the PTO clutch is engaged or not. Also thinking it could be the splined coupling #1 (AR935R) as I have had to replace that on the fan shaft/power
steering.

I don't think so. On some 2 cylinders there was a third length to the drawbar and if put in that spot will make the hammering while turning as the length is not correct. I have no idea what that extra hole is for. Short length is for tillage, long for PTO work, middle no idea but will make PTO problems but still can be hooked up.

And on some of the Deeres the hitch is in proper position not centered to tractor but off to right a bit and there are special holes in drawbar support to corectly position it as the PTO is not centered to tractor. So with a non centered PTO if you try to use a centerd hitch point it makes shaft run at angle and will do the knocking. The 38 A, 46 B & 50 AR were centered, the 49 B and 51 A were not centered. Took us quite a while to figure out correct hitching on them.