Tractor Shakes when PTO is engaged and RPMs are low

[GeoHorn]

There seems to be some confusion about this description of the “problem”.

Does the wobble occur ONLY if a rotary-cutter (so-called “bush hog”) is being engaged by the PTO..??
Or does the wobble occur EACH AND EVERY time the PTO is engage REGARDLESS of an implement being attached…??

And… I think the transmission operating temperature is a red-herring. Hydraulic oil will heat up when work is accomplished. It is a fairly good estimate to expect 100-degrees added to ambient…. another is to expect slightly less than the engine coolant temp.
But placing your hand or spitting on it is a bit of a subjective method of measuring and not to be relied upon…. use an accurate method such as sticking a BBQ thermometer down the dipstick-tube or an infrared thermometer while it is running. (Heat will increase somewhat for several minutes after a shut-down.…and is not the actual running-temperature.)

(It’s going to be an expensive tear down allright…. especially if for nothing accomplished because there’s nothing wrong.)

 

[vft2003]

It only wobbles if something is connected doesn't matter what. Even the dyno machine at the Kubota dealer

 

[NHSleddog]

Every PTO attachment I have has a "wobble" at some low RPM and they all have a "sweet spot" at high RPM. It seems like they all have their own natural "frequency, harmonics etc.".

If it is a new problem, check the balance of the implement (blades, wheels, hammers, drills etc.). A little out of balance can cause a big vibration.

 

[vft2003]

Any idea what would be causing

There seems to be some confusion about this description of the “problem”.

Does the wobble occur ONLY if a rotary-cutter (so-called “bush hog”) is being engaged by the PTO..??
Or does the wobble occur EACH AND EVERY time the PTO is engage REGARDLESS of an implement being attached…??

And… I think the transmission operating temperature is a red-herring. Hydraulic oil will heat up when work is accomplished. It is a fairly good estimate to expect 100-degrees added to ambient…. another is to expect slightly less than the engine coolant temp.
But placing your hand or spitting on it is a bit of a subjective method of measuring and not to be relied upon…. use an accurate method such as sticking a BBQ thermometer down the dipstick-tube or an infrared thermometer while it is running. (Heat will increase somewhat for several minutes after a shut-down.…and is not the actual running-temperature.)

(It’s going to be an expensive tear down allright…. especially if for nothing accomplished because there’s nothing wrong.)

Everyone seems to think I'm imagining it getting too hot. I've had this tractor for 8 or 9 years. I used to run a brush hog all day with no heat problems. I realize it gets hot when you run it. But it should not get as hot as it is. My brother ran the brush hog for two hours and the hydraulic oil got hot enough to melt the rubber end caps completely off the hydraulic hoses.

 

[paugambi]

Any idea what would be causing


Everyone seems to think I'm imagining it getting too hot. I've had this tractor for 8 or 9 years. I used to run a brush hog all day with no heat problems. I realize it gets hot when you run it. But it should not get as hot as it is. My brother ran the brush hog for two hours and the hydraulic oil got hot enough to melt the rubber end caps completely off the hydraulic hoses.

I don't have any experience with this problem in specific, but knowing what a failed bearing on a trailer wheel looks and feels like, it seems like you have some excess friction, like the Kubota tech said, from a failed bearing. A trailer wheel hub can get red hot at night if you don't notice it quickly. I may be wrong, I am not a trained tractor mechanic, but I know enough to be dangerous

Although like many people here have been saying, my M9000 (hydraulic clutch) does a wobble at low RPM's on the bush hog. So I wouldn't worry about the wobble as long as it goes away when you spin it up. Heat like that is def a problem as you know, sadly looks like you will have to get inside and figure out what to replace.

 

[ruger1980]

I would pull the hydraulic filters and cut them open to inspect for signs or wear. If you see excess metal you can assume something is coming apart inside.

Hyd or transmission oil is designed to run at or about 180F a good range is 170-200F. Once you get to 220 or above then you start to degrade the oil quicker.

 

[vft2003]

I don't have any experience with this problem in specific, but knowing what a failed bearing on a trailer wheel looks and feels like, it seems like you have some excess friction, like the Kubota tech said, from a failed bearing. A trailer wheel hub can get red hot at night if you don't notice it quickly. I may be wrong, I am not a trained tractor mechanic, but I know enough to be dangerous

Although like many people here have been saying, my M9000 (hydraulic clutch) does a wobble at low RPM's on the bush hog. So I wouldn't worry about the wobble as long as it goes away when you spin it up. Heat like that is def a problem as you know, sadly looks like you will have to get inside and figure out what to replace.

Thank you, you are probably right like some others have suggested the wobble probably has nothing to do with the heat problem and maybe not an issue at all.

 

[vft2003]

I would pull the hydraulic filters and cut them open to inspect for signs or wear. If you see excess metal you can assume something is coming apart inside.

Hyd or transmission oil is designed to run at or about 180F a good range is 170-200F. Once you get to 220 or above then you start to degrade the oil quicker.

I changed the hyd oil and filter when I started having this problem. It was my first time, the tractor has less than 400 hours. there were metal shavings on the magnet in the filter. Idk what is excessive since that was the first one I've seen.

 

[MOOTS]

I changed the hyd oil and filter when I started having this problem. It was my first time, the tractor has less than 400 hours. there were metal shavings on the magnet in the filter. Idk what is excessive since that was the first one I've seen.

This was my MX6000 at 125 hours.

 

[GeoHorn]

vft …do you have any measurement of how “hot” it is other than your hand and spit?
I’m not trying to be critical…. I’m trying to help you. HOW hot is the oil? What temperature?

 

[vft2003]

vft …do you have any measurement of how “hot” it is other than your hand and spit?
I’m not trying to be critical…. I’m trying to help you. HOW hot is the oil? What temperature?

yes I shot it with a laser thermometer and it was 234f

 

[GeoHorn]

yes I shot it with a laser thermometer and it was 234f

Well.. you’re right… that’s certainly “HOT”.

 

[BruceP]

There is NO WAY the fluid can get that hot without doing "work".

I still contend that there is some kind of hydraulic load which is turning engine-power into heat. (overpressure bypass valve not opening...etc)

I would suggest having a competent hydraulic mechanic hook up guages and find the problem. There should be 'test ports' at key points within the system.,

 

[RCW]

yes I shot it with a laser thermometer and it was 234f

That is really hot. Too hot. It's a great thing you actually take temps.

 

[daves31]

I would think if the pto has a wobble that it has extra stress somewhere (bearings maybe like was already mentioned.) I would also think that would cause the tractor to work harder causing the added heat.

 

[GeoHorn]

A bearing giving problems will not last long without adding metal to the hydraulic filters.
Pull the filters and cut them open and also examine the magnets.