I don't know what an air blast sprayer is, but I have used a lot of 540
rpm pto equipment and I have never had that sort of an issue with the
PTO shaft itself.
My guess is that the problem is deeper inside the machine and not
really related to the PTO shaft at all.
If you are repairing it "for about the fifth time", It sounds as
though you haven't ever gotten to the real problem.
Could you contact the mfr about it or a dealer? It may be a common
problem.

I guess you have a lot more modern tractor than any of mine. My 60 Hp
Case 800 diesel only goes 1450 rpm's at 540 PTO speed.
Have you really checked PTO speed? Could it be that you are over
revving the sprayer?

Pete Stanaitis
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Karl Townsend wrote:
I'm repairing the same issue on my airblast sprayer for about the fifth
time. Own something long enough and the same problems keep repeating. the
sprayer has a vibration in it at 2500 tractor RPM, 540 PTO RPM. The
vibration is not like a tire out of balance but its a bucking forward to
reverse. When it gets a little lose, in a few more hours of run it will damn
near shake the tractor off the ground. Its also a natural harmonic at this
RPM, slow down and the vibration goes away. Unfortunately, this REALLY
reduces sprayer performance.

I'm replacing the entire PTO shaft and tightening up the clearance in the
gear box again. if everything is tight, the problem is less severe. The is
working on the symptom, not the cause.

This is a long shot, anybody know about balancing this sort of vibration or
changing the natural harmonic frequency?

Karl