Uncomfortable noise on finish mower

[dnw64]

I recently bought a used Land Pride FDR1660 finish mower.

It seems to operate nice when relatively flat, but if you lift the deck while it's operating, or go into a bit of a gulley that lifts it on the 3pt it makes a noise/feeling that something isn't right. It's not real lout, but kind of a rumble, or low growl.

I had to get a new PTO shaft for it, so my first thought was that I hadn't shortened it enough, but after double-checking, I still have 3-4" of play when fully raised.

I then checked the gearbox oil - clean and clear and within the min/max lines on the dipstick.

I put a hand on each of the three blades and yanked them about, and all the bearings seem normal.

Anything I should look further into, or is that an accepted factor of one of these mowers?

 

[Industrial Toys]

IS the noise when the pto is at sharp angle? Are the yokes in line? Most newer shafts won't even allow you to misalign the yokes. Although most pto noise is a vibration or shudder, not so much a rumble.

Beyond that, it makes no sense that the noise is position dependent. The only thing changing is your pto shaft.

 

[woodlandfarms]

It could be that what you are mowing is muffling the machine noise... but I.T. seems to have a better thing to check first.

 

[Oldoak]

I would say the issue is in the PTO drive shaft yokes. Either failing or phasing.



Most drive shafts are designed so that they can't be assembled wrong but some with square shafts can.

 

[dnw64]

IS the noise when the pto is at sharp angle?

Not what I would call "sharp". The shaft is pretty long, and it's near dead straight in operation.

Are the yokes in line? Most newer shafts won't even allow you to misalign the yokes.

Not sure how to check/answer that question. This is a triangular shaft that only goes together one way.

Although most pto noise is a vibration or shudder, not so much a rumble.

"Shudder" may be closer, but I would still say it's stronger than a shudder, although maybe not quite a "rumble". Hard to define using subjective words.

 

[dnw64]

I would say the issue is in the PTO drive shaft yokes. Either failing or phasing.

Most drive shafts are designed so that they can't be assembled wrong but some with square shafts can.

This is a brand new PTO shaft, so not likely to be failing. Also unlikely to be assembled wrong, as I'm pretty sure it can only go together one way - it's triangular and IIRC it has a little bump on one of the corners.

 

[Industrial Toys]

The fact that the shaft is long and straight in operation is the preferred arrangement.

MAYBE, you just have a harmonic. Something just hits resonance. Usually the frequency varies slightly up and down, not staying at one exact frequency.

I have found that Diesel Engine vibration can find it's way quite a distance into implements.

 

[Oldtink]

I think I know what you are hearing and it is vibration in the PTO shaft caused by the difference in angles of each U joint. If you connect your top link to the pivoting connection on the finish mower, as you should, and then raise the 3ph, you'll see it does not come up level and that puts the Ujoint at the mower end of the shaft at a steeper angle than the one at the tractor end of the shaft. That causes a vibration. If the two angles are the same the vibrations cancel each other out as when you are on level ground.
PTO Shaft Geometry :: John Deere TechTalk – The Source for John Deere Technical Information
Driveshaft Angle and Phasing - YouTube

 

[dnw64]

I think I know what you are hearing and it is vibration in the PTO shaft caused by the difference in angles of each U joint. If you connect your top link to the pivoting connection on the finish mower, as you should, and then raise the 3ph, you'll see it does not come up level and that puts the Ujoint at the mower end of the shaft at a steeper angle than the one at the tractor end of the shaft. That causes a vibration. If the two angles are the same the vibrations cancel each other out as when you are on level ground.
PTO Shaft Geometry :: John Deere TechTalk – The Source for John Deere Technical Information

Very interesting. It seems like the answer provided in the link above is kinda complicated, and would be difficult to implement on a 3-pt setup (as opposed to drawbar, which it seems they are referring to). First I will check and see if the angles are equal. If not, I wonder if/how much I could adjust it with the top link. Also, I believe there may be two attachment points on the mower, essentially changing the length and potentially the angle according to that article.

I will also double-check the phasing but am pretty sure (unless defective from the factory) that it can't be put together wrong.

 

[dnw64]

I think I know what you are hearing and it is vibration in the PTO shaft caused by the difference in angles of each U joint. If you connect your top link to the pivoting connection on the finish mower, as you should, and then raise the 3ph, you'll see it does not come up level and that puts the Ujoint at the mower end of the shaft at a steeper angle than the one at the tractor end of the shaft. That causes a vibration. If the two angles are the same the vibrations cancel each other out as when you are on level ground.
PTO Shaft Geometry :: John Deere TechTalk – The Source for John Deere Technical Information
Driveshaft Angle and Phasing - YouTube

So... I checked stuff out tonight.

The PTO shaft can only go together one way, and it appears to be in phase.

The link above seems to refer to "pulled" implements as opposed to those "hard mounted" via a 3-pt system. Can't really change anything with a 3-pt.

However, I do see the possibility of the angle changing when the 3-pt link is raised. It seems possible for it to have been designed to eliminate or at least minimize any change, but I don't have the technology to measure/check/verify the change in angles as it lifts. I guess I will have to assume it changes enough to cause this issue, and unless someone can educate me otherwise, accept it as part of "normal" operation. And try to minimize the frequency of such state.