Rotary Cutter Bush hog blades won't turn

[AnnaB264]

I already searched for similar threads, but didn't find anything that applied. I have an old rotary mower (King Kutter maybe? Not sure). It looks a mess, but worked fine until I was doing a heavy field of brush, and no doubt hit something. (I should also note that I committed a mortal sin and had let the gearbox run out of oil. This may be the answer).

I checked that the stump jumper hadn't been knocked loose and was sufficiently tight, and saw the shear bolt was still in place. I noticed that the blades would catch and spin a little at times, but with no force. So I pulled apart the gear box and saw what MIGHT be stripped gears, but although clearly they had been rubbing, it seems to me they should still be catching okay. So clearly I destroyed something here, but I don't know what. Here are a few pics for reference.

 

[Have tractor did travel]

I agree that the gears should still be catching. Do you have another PTO shaft you could interchange ? That would eliminate the possibility of the problem being with the shaft or where the ends engage. Remember, the 2 piece shaft should have 6" of engagement, one piece to the other, when in use. And you don't want much more than that for fear of forcing the PTO into the gear case of the tractor.

 

[wirlybird]

It may seem silly but remove the shear bolt to make sure it really is ok. I've had an end stay stuck in the hole. Having both stay in the hole seems unlikely but you just never know.
In trouble shooting start with the most obvious first. A process of elimination.
Shear bolt ok?
Is the PTO shaft turning the input shaft on the gear box? Then work from there.
Also, remove the stump jumper to make sure the center splined part is still attached. Had a stump jumper break free from the center splined part but stay in place.

 

[AnnaB264]

I agree that the gears should still be catching. Do you have another PTO shaft you could interchange ? That would eliminate the possibility of the problem being with the shaft or where the ends engage. Remember, the 2 piece shaft should have 6" of engagement, one piece to the other, when in use. And you don't want much more than that for fear of forcing the PTO into the gear case of the tractor.

I think the PTO shaft is fine... the cover has mostly torn off, so I can see it turning at both ends. Is there anything else I should be looking for?

 

[AnnaB264]

It may seem silly but remove the shear bolt to make sure it really is ok. I've had an end stay stuck in the hole. Having both stay in the hole seems unlikely but you just never know.
In trouble shooting start with the most obvious first. A process of elimination.
Shear bolt ok?
Is the PTO shaft turning the input shaft on the gear box? Then work from there.
Also, remove the stump jumper to make sure the center splined part is still attached. Had a stump jumper break free from the center splined part but stay in place.

I did remove the shear bolt to check it, and it's fine. It seems the PTO shaft is turning the input shaft, I will look again and make sure. How do I remove the stump jumper? And what is the center splined part? I have learned pretty much everything I know about tractors and equipment via this website and Google! Thanks for your help.

 

[wirlybird]

This is a typical stump jumper. It goes up onto the shaft that comes out of the gear box. It is held on by a large castle nut (pictured). Then the blades bolt to it.
To remove it you'll need to be able to access the underside of the brush hog. This is dangerous so get help and make sure to position the brush hog so you can work on it without a chance it can fall. I usually tip mine up on its side so it leans against a couple trees. A tractor with loader can be used to flip it over. Once you have access to the underside you can just look at it to see if it seems ok where the two parts are welded together.
You want to check to see if the round part (splined part at the center) is still welded/attached to the disk part. If it looks ok then once you can safely get to the underside you can see if rotating the input shaft causes the output shaft to turn.

 

[mcfarmall]

Additionally, the output shaft and the stump jumper have a tapered spline. You might get the castle nut off easily but will have to fight breaking the taper loose. Doesn't grab like a Morse taper but pretty close to it.

 

[ZetorSteve]

The teeth on the blade shaft gear are damaged from your picture. It's new gear box time. Good news is they are cheap on ebay. Around 160 bucks shipped. The 40hp boxes on most light duty cutters are all the same. Remove the stump jumper and count the splines. I bet there is 12 splines.

 

[AnnaB264]

This is a typical stump jumper. It goes up onto the shaft that comes out of the gear box. It is held on by a large castle nut (pictured). Then the blades bolt to it.
To remove it you'll need to be able to access the underside of the brush hog. This is dangerous so get help and make sure to position the brush hog so you can work on it without a chance it can fall. I usually tip mine up on its side so it leans against a couple trees. A tractor with loader can be used to flip it over. Once you have access to the underside you can just look at it to see if it seems ok where the two parts are welded together.
You want to check to see if the round part (splined part at the center) is still welded/attached to the disk part. If it looks ok then once you can safely get to the underside you can see if rotating the input shaft causes the output shaft to turn.

View attachment 711755View attachment 711756

Thank you, this is very helpful! I did flip it over to make sure the castle nut was tight (used my FEL, as I saw demonstrated on YouTube). I can do that again and check the weld, as well as the input shaft turning the output shaft. I'll try it tomorrow and see what I find. Thanks again.

 

[cathy liebchen]

Needs new gear box and keep oil in it