Why do PTO drive shafts have grooves?

[K5lwq]

Didn't some of the very early tractors with a PTO have a hole through the shaft so you could pin the mating parts together ??

I think many have the hole but I think it was for adapters to different type shafts or overrun clutches. Had a 5/16" hole if I remember correctly.

 

[JWR]

Didn't some of the very early tractors with a PTO have a hole through the shaft so you could pin the mating parts together ??

Certainly did. My family heirloom 1954 Massey-Harris Pacer has 1 1/8 " PTO with no groove for drive shaft U-joint retention. It has a hole for a pin to keep the pulley (typically a pulley) on the PTO shaft. No idea what the diameter was supposed to be but we used a 1/4" bolt. Those PTOs had no over-run free-wheeling so an attachment with a big flywheel effect could shove the tractor as somone else mentioned. A fairly heavy 4ft bush hog would also break off the PTO shaft and or bust gear teeth inside the PTO drive too. For that reason, TSC and others sell an over-run clutch that fits over the PTO and provides a Std 1 3/8" 6 spline shaft as seen by external attachments. Tried once without the overrun clutch and then went hunting for a parts yard with an old Pacer to pull one off of. Eventually found one to fit.

 

[dougtrr2]

Ahh I see. Sorry for newbie question. Never attached a pto before.

Since you admit to being a newbie (like we all were at some point) I just want to point out something that has not been directly mentioned.

Make sure your PTO collar locks into that groove. You can slide it on and not snap into the groove if you don't get it on far enough. You should be able to hear or "feel" it snap in. If it doesn't lock on and comes off the carnage could be substantial.

And welcome to the forum

Doug in SW IA

 

[JWR]

dougtrr2 is exactly right. You should be able to tug on the drive line U-joint and not be able to pull it off the PTO. These things are not much fun in the best of times but suggest trying it several times, lube the PTO and the U-joint, then see what it feels like -- both to be on fully and to be "still loose" and coming back off the shaft.