thwacking noise from deere 455 w/60 inch mower

steve74 · May 26, 2016

So I got the lift issue sorted out adequately (I think) but shortly after I started mowing yesterday the mower started making a mild but persistent intermittent thwacking noise. It was audible, but dull and not not transmitted as a noticeable vibration, and seemed harmonic - it would do it for 10 or 15 seconds, then stop for a little, then come back. Initially I thought there was a helicopter passing by in the distance but when it persisted I killed the PTO and it stopped. It didn't seem to change or get worse, so I finished mowing. Definitely PTO related - doesn't do it just running around.

Checking later there was some play in the PTO shaft, but it didn't seem loose. I assume there has to be some play. The belt looks good, and none of the blades seem to wobble so I think the spindles are fine.

Anything else I should be checking or testing? Is this common?

Thanks
Steve

oldnslo · May 26, 2016

Is there enough grass build up under the deck so one of the blades could be hitting it? Possible belt is flopping slightly or idler bearing getting rough?

Richard001 · May 26, 2016

Steve,

Did you check the belt all the way around? Could be a chunk missing from the inside of the belt.

Check your idler pulleys and the spring tension.

Also did you try changing the rpm? Did it make it go away or make it worse?

Richard

steve74 · May 26, 2016

Thanks. The deck was clean, and I blew some dry grass out from the belt area but it wasn't particularly bad.

I checked the belt but didn't actually take it off. Could be a chunk missing that I couldn't see. And the idler bearing is a good thought - I suppose when I take the belt off would be a good time to check on that.

kthompson · May 26, 2016

Could be picked something up under the deck also. I will also add you could have a belt coming apart and you may not see that till it happens. Had that on deck two years ago. Really was glad when it fail for turned out replacement belt was quite.

beenthere · May 27, 2016

I'd guess you have a loose or bent piece of steel that is tack welded around the inside of the deck, just near the tips of the blades. That, or a bent blade or other lose part.
Flip the deck over and look for the shiny part.