I don't know enough about modifications guys do for making pullers......might be somebody messed with the gearing somehow, but sort of doubt it. Don't even know if that would ultimately affect PTO speed or not.

Hurst

Nope. My dad ran the Allcrop and bar mower at 540. He would check shaft with "end tach" and pay attention to where that was on the quadrant. Not much else would matter I think.

I'd check the spreader.  Some of them can run 540 or 1000.  They flip the drive belts to a different set of pulleys to keep the spinners at the same speed.  If it's set for 1000, but has a 540 shaft, it's going to do what you say its doing.

AaronSEIA

Well, yes, it depends on the implement.  But I would say, I run several things slower than 540, such as unloading wagon, elevator as you mentioned.  Also do not run manure spreader full speed, I mean, why?  To throw it farther?  Not an important consideration for me.  We have also NEVER run a small square baler at 540, got the rhythm in my head, but couldn't tell you actual RPM, definitely slower than 540.

Forage choppers, blowers, round balers, etc., run at 540.  I guess that's because most of the tractors I grew up on had the PTO mark on the tach where WOT was anyway.  My big Allis will "overspeed", and the tach doesn't work anymore, usually put it where it sounds right, not quite wide open.  I suppose the chopper might run a little faster now days....it's a 1000 RPM unit, tach hasn't worked since before we bought it, want to fix that dang tach one of these days.