456 New Holland mower

[72supr]

Mower is in excellent condition I’ve had it for forty years.It keeps breaking the bolt in the drive line. Not a shear bolt it just holds the drive line together. I thought at first the hole might have had wore funny but it hadn’t. Anyone have an idea?

 

[Destroked 450]

I assume this bolt holds a yoke onto the drive line

 

[Jim.ME]

A picture showing the driveline and where this bolt (size?) is in the driveline might help.

 

[Phill Tibbetts]

Mower is in excellent condition I’ve had it for forty years.It keeps breaking the bolt in the drive line. Not a shear bolt it just holds the drive line together. I thought at first the hole might have had wore funny but it hadn’t. Anyone have an idea?

Are you using the right bolt as far as grade?

 

[rrlund]

Have you slid it off to see if there's supposed to be a key in there? I can't imagine that there's not.

 

[72supr]

It’s a square shaft so wouldn’t be keyed. 1/4 inch grade five bolt is what is called for. No slop in the shaft or yoke. On the mower it is the only junction on the driveline. Not to good at loading pictures but I’ll try

 

[Jim.ME]

Is this a drawbar pull mower, not a 3-point hitch? If this is a shaft that is on a support to go along with a sliding section of shaft, it is possible the bolt is shearing because the travel of the shaft is binding and the yoke is moving easier than the entire shaft, shearing that yoke lock bolt.

 

[rrlund]

Is this a drawbar pull mower, not a 3-point hitch? If this is a shaft that is on a support to go along with a sliding section of shaft, it is possible the bolt is shearing because the travel of the shaft is binding and the yoke is moving easier than the entire shaft, shearing that yoke lock bolt.

Exactly what I'm thinking. Binding under load. When I first got my Hesston 1120 brand new, if I raised it while it was still running a heavy slug through the rolls, it would pull the bearing in the driveline right out of the flanges.

 

[Roger in Iowa]

If drawbar of tractor set short it may bottom out the driveline causing bolt to shear.

 

[Jim.ME]

It’s a square shaft so wouldn’t be keyed. 1/4 inch grade five bolt is what is called for. No slop in the shaft or yoke. On the mower it is the only junction on the driveline. Not to good at loading pictures but I’ll try

Pictures of this driveline please. It would aid greatly in helping you.

 

[paul]

As others mention, assuming this is a sliding pto shaft is it rusty, twisted, bent, dented, otherwise no longer sliding easily?

Or bottoming out?

Paul

 

[DanielW]

Agree with all others. Pictures would be good: I have one of those mowers and can't picture what bolt you mean for sure. But I'm guessing it's this bolt in the PTO driveline - one that holds the yoke to the square shaft? I'd bet dollars to buttons your shaft is either binding up or bottoming out when you make a turn. Very important to make sure telescoping PTO shafts are free-sliding through their full stroke and not bottoming out when you turn or lift the implement: If it binds or bottoms out, it puts a holy heck-load of axial force in driveline components of both the tractor and implement, none of which were designed to take any axial force. Oodles of gearboxes and PTO shaft bearings have been pooched because of the telescoping part of PTO shafts binding/bottoming-out.

 

[72supr]

Here is mower Bolt is right below carrier. Everything slides freely.

 

[Jim.ME]

Is this the first year it has been breaking the bolt? Are you using the grade 5, 1/4"-20 x 2-1/2" bolt?

Are the U-joints all in time?

Do you have the washer (#29) that is supposed to be behind the yoke? If there is excess play back and forth between the yoke and shaft that could be a contributing factor.

What is the condition of the bearing assembly and the parts on the other side of the bearing? Has it ever been rebuilt in 40 years?

How are the u-joints?

Something pulling and putting a strain on the bolt would be a cause, that was the question of how freely things slide. The shaft from the tractor binding in a turn or the bearing support twisting in a corner could put a strain on the bolt, more so it the spacer washer or other such part missing from the bearing assembly could allow the shaft to move in the bearing more than the bolt can accept.

 

[72supr]

It happened last year when cutting wild hay. It calls for 1/4 inch but drilled it out to 5/16 last year but still breaks bolt. Joints are good.I’ll check for that washer

 

[DanielW]

It looks like that shaft and the square bore in the yoke is worn some. How tight a fit is the shaft in that square bore? It should be fairly tight. You want the square bore and shaft taking the torque load, not the bolt. If the shaft/bore is worn too sloppy, the bolt will be taking the torque before the shaft comes again the yoke bore. Might require a little careful weld build-up and grinding.

 

[72supr]

It’s tight.Washer is there.

 

[ss55]

Mower is in excellent condition I’ve had it for forty years.It keeps breaking the bolt in the drive line. Not a shear bolt it just holds the drive line together. I thought at first the hole might have had wore funny but it hadn’t. Anyone have an idea?

When the bolt shears the middle potion might stay inside the shaft and might even have to be knocked out with a punch. Can you look at the destroyed bolt to determine if the bolt sheared from torque overload ( radial marks in the direction of rotation ) or if the bolt sheared along the length of the shaft ( axial marks ) ?

If the telescoping potion is nearly fully compressed, sometimes going through a dip or starting up a steep incline can cause the telescoping shaft to bottom out solid, putting the entire shaft under a high compression load. Do you remember what was happening when the bolt sheared?

 

[72supr]

Thanks for the replies. But still have no solution