RC72 Mower Deck Vibration

[JPinnell]

So I have a 72in Mower Deck I bought with my new Kubota B7800 approx 15yrs ago. I've not had a lick of trouble with the tractor or mower. Money well spent. Approx 850 hrs on the tractor and half or a bit better, say less than 600hrs mowing? But this mowing season I've noticed a little more vibration from the deck. I'm pretty good about keeping it greased but given the age something is up.

So I pulled the blades and swapped them. Checked the oil and the gearbox was not dry, still correct level. I cleaned up the PTO shaft, Joints seem tight, no noticeable play in the splined shaft. I did find a baffle had come loose and looked like it might be kissing a blade as there was a bright wear spot. So I clamped that down and welded it back. Pulled the belt (the 2nd about 5yrs old) and spun all the spindles by hand without the blades mounted. They spun freely, did not feel dry, no drag.

So i put it all back together. Mounted the deck and mowed. Still a vibration. So run it until it really breaks? I figure its the PTO Shaft somewhere but that's $750. Any thoughts?

 

[LS Tractor Owner]

Any possibility that it hit something and slightly bent a spindle shaft?
I would imagine that you would see a difference when hand spinning the blades.

Are the blades relatively balanced? I had some old blades that were sharpened many, many times. One was definitely out of balance and caused a serious vibration.

Hope you're able to figure it out.

 

[LS Tractor Owner]

You may want to check the torque on the stump jumper nut.

It's a finish mower.... no stump jumper.

 

[BleedingOrange]

To help isolate your problem, can you remove all the blades and run it up to speed to see if the vibration is still there, or not ?

 

[5030]

I'd say the blades are basically shot and out of balance, I replace mine every other year no matter how many hours and your hours are excessive...

 

[JPinnell]

I put a new set of blades into rotation at least every other year. Sometimes once a year. I run the Gator Mulching Blades and mowing leaves in the Fall seems to have the most wear. I pitch them when the tips get too rounded as then they leave a tuft in the center thats not cut. I've got 3 sets of blades and swap them a few times a season.

This is the "new" set from last Fall with the carbide. Blades are not overly worn, fairly well balanced when hung/spun from a nail. No obvious bends etc. I will remove the blades and run it up to speed and see if the vibration changes.

 

[mikester]

If the belt is starting to delaminate you will get vibration

 

[ruffdog]

If a ball bearing cage has come apart, the inner race may not run concentric to the outer race. This would allow the mower spindle to not run true and would shake. If this is the case, it won't last long.

 

[milkman]

A while back, I replaced the belt on my ZD21 and noticed some slack in the geabox that I hadn't had before. The last time I mowed, I noticed that I could feel some vibration in the footwell.
There's not any unusual noise and the gearbox is not getting hot, but I ordered the bearings and seals to rebuild the gearbox. Hope yours is an easy fix.


















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[LS Tractor Owner]

I put a new set of blades into rotation at least every other year. Sometimes once a year. I run the Gator Mulching Blades and mowing leaves in the Fall seems to have the most wear. I pitch them when the tips get too rounded as then they leave a tuft in the center thats not cut. I've got 3 sets of blades and swap them a few times a season.

This is the "new" set from last Fall with the carbide. Blades are not overly worn, fairly well balanced when hung/spun from a nail. No obvious bends etc. I will remove the blades and run it up to speed and see if the vibration changes.

Yes, that would be a good way to eliminate if it's the blades. You might be able to see if a spindle is wobbling with no load / centrifugal force on them. Keep us posted with the results....