Bush Hog violently shaking

[lwarner901]

I just got the seal on my gearbox replaced & brand new blades. Woods 10’ cutter with 3 point hitch, took it out today and worked so well, until I crossed a ditch that had washed out during the winter and was deeper than I thought. My husband had to get the shovel to dig me out. Them when I turned on the PTO to start cutting that field, the cutter shook VIOLENTLY. What happened and how do we fix it? Please!!!

 

[Hay Dude]

Look underneath to see if a clump of dirt is stuck to blades, stump pan, spindles, etc.
Don’t take much to make them shake.
If thats all clean, check for a bent blade, stump pan, spindle, etc.
If that all checks out, start working from the cutter back to the tractor and look for anything bent or not running “true”.

 

[lwarner901]

Thank you! We just raised it and looked for dirt clumps on the stump jumpers, no dirt, spun the blades, they seem to be ok. Slid the PTO shaft in and out, no bends. We’ll keep looking

 

[lwarner901]

Look underneath to see if a clump of dirt is stuck to blades, stump pan, spindles, etc.
Don’t take much to make them shake.
If thats all clean, check for a bent blade, stump pan, spindle, etc.
If that all checks out, start working from the cutter back to the tractor and look for anything bent or not running “true”.

Thank you! We just raised it and looked for dirt clumps on the stump jumpers, no dirt, spun the blades, they seem to be ok. Slid the PTO shaft in and out, no bends. We’ll keep looking

 

[Hay Dude]

Did you hit something like real sudden and stall the tractor real quick?
Or did you just bottom out the mower and it kept running?

 

[lwarner901]

Did you hit something like real sudden and stall the tractor real quick?
Or did you just bottom out the mower and it kept running?

Did not hit anything suddenly, I turned the PTO off before crossing the ditch & raised the hitch up as high as it would go, went into the ditch, back tires got stuck in the ditch, front tires on the way up the other side, cutter on the slope down, and spun out. Tried the 4WD and shift diff,,, then called husband who dug out in front of front tires and came out. Can not see anything that is bent,,, can not figure this out.

 

[lwarner901]

Did not hit anything suddenly, I turned the PTO off before crossing the ditch & raised the hitch up as high as it would go, went into the ditch, back tires got stuck in the ditch, front tires on the way up the other side, cutter on the slope down, and spun out. Tried the 4WD and shift diff,,, then called husband who dug out in front of front tires and came out. Can not see anything that is bent,,, can not figure this out.

No mud in the pans, underneath looks clean, PTO shaft not bent

 

[Hay Dude]

I wonder if the steep up angle coming out of the ditch bent something on your PTO shaft stub on the mower

 

[lwarner901]

No mud in the pans, underneath looks clean, PTO shaft not bent

No mud in the pans, underneath looks clean, PTO shaft not bent

I wonder if the steep up angle coming out of the ditch bent something on your PTO shaft stub on the mower

I unhooked the cutter, and pulled the PTO shaft in and out and it slid perfectly. Oh! The stub on the mower,,, that’s hooked to the middle gearbox,,, how can I tell if it’s bent?

 

[DJ54]

Did you happen to notice one of the blades folded forward, but not stuck in place like with the sharpened side towards the pan when you checked the blades..?? If you had to pull the blade so it's straight out like it should be, then spun, that could have been the problem, knuckled ahead, and it makes it hard for centrifugal force to straighten out to cut and makes it unbalanced.

 

[Hay Dude]

That’s not as easy. I’d pull the shielding off and hook PTO shaft back up, then slowly spin up the mower at low rpm and take a look at the stub. See if it wobbles.

When you say “PTO shaft not bent”, did you remove the plastic shielding? It could be bent under the shielding.

 

[lwarner901]

Did you happen to notice one of the blades folded forward, but not stuck in place like with the sharpened side towards the pan when you checked the blades..?? If you had to pull the blade so it's straight out like it should be, then spun, that could have been the problem, knuckled ahead, and it makes it hard for centrifugal force to straighten out to cut and makes it unbalanced.

Awesome thought! I will pull it back up in the morning and check that!

 

[sandman2234]

I have had blades cross and get stuck before. Spinning them while crossed and they shake violently, but usually come uncrossed and all the vibrations stop.
David from jax

 

[jfsawatzky]

I have had blades cross and get stuck before. Spinning them while crossed and they shake violently, but usually come uncrossed and all the vibrations stop.
David from jax

Similar to the above comment, I managed to bind some small piece of wood between the blade and housing that caused one blade to stop rotating and throw it off balance. Was a pita to remove that piece of wood.

 

[Hay Dude]

If you tried to climb out of a steep ditch and the prop shaft had no more room to go up, you could have tweaked something. One way to eliminate the tractor is to hook the BH up to another tractor. But I think its something in the BH, starting at the blades and up to the prop shaft.

To eliminate your tractor, hook something else up to it and see if it shakes that attachment.

 

[Fladogman]

I would try disconnecting the drive Link lift the mower , crawl underneath and spin the blades and look for some out of place first

 

[lwarner901]

That’s not as easy. I’d pull the shielding off and hook PTO shaft back up, then slowly spin up the mower at low rpm and take a look at the stub. See if it wobbles.

When you say “PTO shaft not bent”, did you remove the plastic shielding? It could be bent under the shielding.

My PTO shaft is a connected 2 piece one that slides inside the other, I pulled back the plastic shielding and slid it in & out of each other no problem. I’m going to try to hook up another 3 pt this morning AND look underneath again to see if all the blades are turned at the same angle

 

[Hay Dude]

My PTO shaft is a connected 2 piece one that slides inside the other, I pulled back the plastic shielding and slid it in & out of each other no problem.

The plastic shielding may slide easily, but the steel prop shaft inside might be slightly tweaked.

I’m going to try to hook up another 3 pt this morning AND look underneath again to see if all the blades are turned at the same angle

What you might want to inspect is the input shaft to the mower.

Also inspect the prop shaft U-joints. When you put the mower on an extreme angle, it may have tweaked a U-joint.

Start with the simple/easy things like bent blades, or blades that are not swinging properly, then move to prop shaft, u joints, then look at the splined input shaft on the mower

 

[jyoutz]

Did you happen to notice one of the blades folded forward, but not stuck in place like with the sharpened side towards the pan when you checked the blades..?? If you had to pull the blade so it's straight out like it should be, then spun, that could have been the problem, knuckled ahead, and it makes it hard for centrifugal force to straighten out to cut and makes it unbalanced.

I suspect that’s what the situation is.

 

[Frxdy]

I tweaked a blade once and it would mostly rotate, but had one spot it would stick. The blade was bent, just a little . I had to remove it to repair.... maybe should have replaced it, but I did get it straight enough to work freely.