Bush Hog 406 (drive shaft slipped off of Gear Box input shaft) Need advise (with pic

[RickB]

The hole in the gear box shaft is for non slip clutch applications, where a shear bolt would be used

Not going to use a 5/16" shearbolt on a 4" rated rotary cutter, nor does one use a through bolt in a splined shaft as a shearbolt. The prior style driveshaft and slipclutch used the through bolt.

 

[RickB]

Rick, I think you are exactly correct. I don't think this could have come apart without doing damage had it been installed properly in the beginning. Several have mentioned that I should inspect the gear box and my tractor to make sure no damage was done when I ran it last year while the shaft was too long. Exactly where and what will I be looking for?

Mine is the only explanation that fits the circumstances.
As to the prior events and potential damage, if the gearbox input shaft and tractor output shaft aren't bent and the seals aren't leaking, you are probably OK.

 

[Jerry/MT]

Well, I just posted 2 days ago about how proud of myself I was for shortening the drive shaft in my Bush Hog 406 and this afternoon I suffered a setback. I was shredding some pretty large brush/trees (approx. 2-1/2 to 3" diameter). I heard a different noise and looked back to find that my PTO shaft had come apart at the gear box. I immediately shut off the PTO and idled down the tractor for inspection. Upon closer examination I found that the drive shaft just rearward of the slip clutch had come off the gear box input shaft. As I mentioned in my post regarding shortening the shaft, I ran this shredder for about an hour last year. Other than that, this is the first time I have run it. It appears that there should be a bolt of some sort going through the male and female portion of the connection. Im not sure if this is a shear pin or a regular bolt. I suspect either one of 2 things happened"

1) The shredder came from the dealer without a bolt/shear pin.
2) My using it last year with the drive shaft being a tad too long put pressure parallel to the shaft and broke the pin/bolt, and using it just vibrated it apart.

Anyway, any and all suggestions and explanations on what I broke and how to fix it are welcomed.

You have to remove the clamp bolt on the slip clutch, slide the female end over the g/b inputshaft splines so the bolt goes through the slot and tighten'er down. I had this happen to me when I was in a hurry and not paying attention.

 

[Bladehauler]

Looks to me like the OP simply loosened the pinch bolts then slipped the shaft on till the bolts butted up to the end of the shaft, then tightened the bolts.
Wrong approach.
The bolts must be completely removed so the clutch yoke can slip over the input shaft to the point where the bolts will engage the groove in the input shaft when installed. Then the bolts will clamp the yoke and sit in the groove completely preventing the shaft from coming off as long as the bolts are in place and tight.
No other parts are needed or used in this installation.

I believe Mr. Rick is right on this one !! yup , pull the bolts ,slip it all the way on the shaft reinstall the bolts so they reference in the grove of the shaft.

Good Eye Mr Rick

 

[Zebrafive]

Not going to use a 5/16" shearbolt on a 4" rated rotary cutter, nor does one use a through bolt in a splined shaft as a shearbolt. The prior style driveshaft and slipclutch used the through bolt.

You are right Rick. I didn't know it was only a 5/16" hole, my BAD.
I was thinking a round tube would slip over a splined shaft, so shear bolt or slip clutch would be options for same gear box.
I also overlooked it was 4" cutter so it would have a slip clutch OOPS!

 

[pharmvet]

Ok, here goes. I know you guys are not going to buy this, (Especially you Rick B. LOL) but its true. I went down this afternoon with my new confidence and knowledge to fix my issue only to find that the 2 bolts located on the sides of the slip clutch yoke do "NOT" engage the groove in the drive shaft. They are located such that they do not extend into the "lands and grooves" of the slip clutch collar. I know its hard to believe, I almost cant believe it myself, but its true. I really, really think this joint originally had a bolt through the hole that I probably broke by operating my shredder with the drive shaft too long and that after the bolt broke, the vibration of use caused it to slip off. All this being said" What size, length and grade bolt should I put back in there???thanks a million.

 

[IkeRoberts]

My common sense just kicked in. Pharmvet, you are right. The bolt stops the clutch from slideing up and down the shaft. It offers no shear protection whatsoever. The spline mates on both parts to turn the gearbox.

 

[Don87]

Ok, here goes. I know you guys are not going to buy this, (Especially you Rick B. LOL) but its true. I went down this afternoon with my new confidence and knowledge to fix my issue only to find that the 2 bolts located on the sides of the slip clutch yoke do "NOT" engage the groove in the drive shaft. They are located such that they do not extend into the "lands and grooves" of the slip clutch collar. I know its hard to believe, I almost cant believe it myself, but its true. I really, really think this joint originally had a bolt through the hole that I probably broke by operating my shredder with the drive shaft too long and that after the bolt broke, the vibration of use caused it to slip off. All this being said" What size, length and grade bolt should I put back in there???thanks a million.

I probably shouldn't even post here, because, I said the same thing Rick did(except that you inferred that the dealer put the PTO shaft on the brushog), in your other thread and you still posted a new thread.

You have 2 bolts on your slipclutch. 1 is for the clamp, the other goes thru your splines inside your shaft.............that is the one you want to look at. Put that bolt thru your slipclutch shaft, and look down the tube. You should see the shank of that bolt, and it should be 'above' the splines in your slipcltch. If it isn't, it is the wrong sized bolt(shank to narrow), if it is sticking above the splines..........it's the wrong shaft for your brushog.

EDIT: the picture you posted in your first post..............the top bolt that you see is the clamp, nothing more. The bolt you see on the bottom is the one that keeps the shaft from coming apart. That's the one to look at. And that's the one I wanted you to pull to see if it had marks on the shank...........I've seen people put the wrong size bolt in there on at least a dozen times.

 

[Don87]

I probably shouldn't even post here, because, I said the same thing Rick did in your other thread and you still posted a new thread.

You have 2 bolts on your slipclutch. 1 is for the clamp, the other goes thru your splines inside your shaft.............that is the one you want to look at. Put that bolt thru your slipclutch shaft, and look down the tube. You should see the shank of that bolt, and it should be 'above' the splines in your slipcltch. If it isn't, it is the wrong sized bolt(shank to narrow), if it is sticking above the splines..........it's the wrong shaft for your brushog.

EDIT: the picture you posted in your first post..............the top bolt that you see is the clamp, nothing more. The bolt you see on the bottom is the one that keeps the shaft from coming apart. That's the one to look at. And that's the one I wanted you to pull to see if it had marks on the shank...........I've seen people put the wrong size bolt in there on at least a dozen times.

And remember, I said 'shank of the bolt' , not threads................you should see no bolt threads at all when looking doen the end of the slipclutch shaft.

 

[Don87]

And you asked about bolt size. If that shaft was made by the manufacturer of your Brush hog(which is highly unlikely), that bolt is listed in there. Your dealer should have given you the owners manual for the PTO shaft. I got a seperate manual just for the PTO shaft.