What Series PTO Shaft do I need?

sgm98z · May 7, 2019

I have a MF 255 that is set up for Cat. 2 implements. I have a Bush Hog mower that is a category 1 and the PTO shaft is too short so I need to replace it. What series of PTO shaft do I need to run the mower? The tractor is 55 hp. I'm thinking I probably need a Series 6 since it's rated for 60+ hp but I wasn't sure if I was missing something since the mower isn't a ground contact implement and maybe doesn't need the heavier series but I obviously don't want to go too light on the shaft and have it break.

CobyRupert · May 7, 2019

I didn't even know there where different classes of PTO shafts. I thought there were different "spline counts" when going from 6 spline 540 rpm pto to a 20 (or 21?) spline 1000 rpm.

Yes, the mower isn't ground contacting (most of the time), and hopefully it's only the slip clutch or shear bolt (and not the pto shaft) that experiences the shock when the mower contacts a stump or rock,..

....and one can make an argument that you'd rather break a weaker pto shaft than have a heavy duty one transfer that shock into the tractors PTO gears if the shear bolt doesn't fail, or the slip clutch does...

......but (IMHO) I'd want a PTO shaft matched to the tractor's horsepower just so the universals are sized to match the possible horsepower you might occasionally be putting through them, and/or have a greater operating margin, and/or longer lifespan. :2cents:

bullbreaker · May 7, 2019

PTO Shaft-PTO Shafts | Agri Supply 9647 You might know how but either way make sure you adjust the slip clutch correctly !!!.... Play safe , have fun !!!

sgm98z · May 7, 2019

Thanks Coby. Great points and much appreciated.

sgm98z · May 7, 2019

Thanks Bull. That's a great price too. Appreciate the info.

oosik · May 7, 2019

My Wallenstein BX62S is the only PTO driven implement I own. I run it with my Kubota M6040 (62 engine hp, 55 PTO hp). The supplied drive line is a Binacchi B5 - rated max @ 70 hp. It has a shear pin rather than a slip clutch. Last time I looked they were around $250. It is a series 5 PTO shaft.

sgm98z · May 7, 2019

Thanks Oosik. Appreciate the info/options.

LouNY · May 7, 2019

There are several styles of pto shafts and several series in each style;
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=27&cad=rja&uact=8&ved=2ahUKEwji-7ir1oniAhVQvlkKHeDKC6wQFjAaegQIBhAC&url=https%3A%2F%2Fwww.vapormatic.com%2F_assets%2Fdocuments%2Fpto%2520catalogue.pdf&usg=AOvVaw0GxSrMKxt0YpfrK0TiaWQW
If this link works it's to a vapormatic catalog for the different current styles it doesn't have the older square tube types.
Every style has its own HP and identifying labeling. One styles 4 rating can be equal to anothers 6

oosik · May 7, 2019

What LouNY says. Within each series there are varying lengths - varying shape of the shaft itself - shear pin or slip clutch & the dreaded attachment "dongle". I checked again and Series 5 has shafts rated from 50 hp to over 100 hp. Some of these shafts can run over $300. I would call Bush Hog - get the answer straight from the horses mouth( one of their product technicians ).

Too much shaft and something other than the shear pin or slip clutch may break. Too little and it will simply be a PITA on pins or the clutch.