You need to remove the blades and lay them on a flat surface,,make sure they are not bent,,I would also have them balanced and sharpened if not bent...could have also bent a spindle shaft if the blades are ok?I was mowing the other day with my 2009 Craftsmans 48" riding mower. Its made by Husqvarna. I hit a tree branch or something while mowing my aunt's property that was buried under some weeds and now there is a slight but annoying vibration coming from the deck area. Almost like one of the blades is slightly rubbing or hitting something.
I looked under the deck. The blades are not loose nor do they appear bent but are quite dull from where I have hit small tree branches this spring. The blades come close to one another. I wonder if when they are moving they might be touching one each other when they come together. Is that possible?
I also could not find anything loose or broken on top of the deck. One of the screws did fall out from one of the plastic pulley guards. I replaced it but it did not fix the problem.
Another thing I noticed was my front yard. But this was before the vibration happened. There are 4" strips about 1" higher than the rest down each pass. I may have to take a photo. Could one end of the blade be dull from hitting tree branches? However I have zoysia grass so if get's somewhat high it looks kind of funky when mowed. It also looks scalped like I had my deck too low. But I had my deck to set to the same level I always do, notch 3. But we have had a dry season so once again this type of grass looks funky when we have a drought.
I'll try to snap a photo of my front yard when I get home.
I've got mulching blades on my mower by the way.
Also if I am sitting on the mower, the support on the rear/right side of the deck is tight but on the other side I can lift up on it. This is the side with the adjustment to set the level. I think that is normal.
When I adjust the level, the deck raises like it should.
BTW, I know you are not supposed to hit small tree branches that this will dull a blade. I'm not trying to abuse my mower but the problem is I could spend all day picking up these branches. Some of them I can't even see in the grass. Anything larger like more than 2" in diameter I pick up and throw over into the pasture or woods but I have so many pine trees, they drop branches like crazy. I can't keep ahead of these tree branches!
I have been at the beach for a week and just got around today at looking at my mowers. Just as well since we are practically in a drought here in East Tennessee so all that has grown in the past two weeks are weeds.
I rotated one of the blades and made a mark with my Sharpie on the inside of the deck then rotated the blade 180 degrees to see if the mark aligned with the other end. It did not. About 1/2" difference.
Well, looks quite obvious that the blade on the right is bent vertically and it does not lay flat. However the blade on the left does lay flat but appears bent horizontally:
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I could not find anything wrong with the spindles. The bases where they bolt to the deck are not broken. I hope they are not bent. Do the spindles bend or just break?
I ordered some new blades. I guess I'll know when I get them bolted on.