Mowing vibration when mower is engaged

mhampton · Nov 10, 2012

I recently aquired a Craftsman GT5000 with the purchase of a house. It looks to be 3-4 years old and seems to be in good shape, been using it twice a week for the past 2-3 months with no problems. Recently I mowed over a small branch (1/2"-3/4" thick) and now there is a vibration while I mow. I looked under the deck and found nothing stuck and cleared everything out as best I could. Blades and belts all seem to be fine. Could the branch have knocked the deck out of alignment or out of balance? It seems that the vibration is worse when I am going up hill and less when going downhill. Any advice before I pull the deck off for closer inspection? On another note the headlights suddenly do not work either, coincidence?

1fastbob · Nov 10, 2012

Could have bent the blade spindle. (the shaft that the blade bolts to that spins it).

creekbend · Nov 10, 2012

I also agree that you should check the blade spindle. I had to replace one on my Craftsman riding mower this past season. Our SIL had run over a rock and the result was a cracked and broken spindle shaft. The part was round $45.00 and it took my SIL and me around an hour to complete the repair. Best wishes.

radioman · Nov 10, 2012

try wobbling the blades. if there is no play in it, on a flat surface then try moving blade around slowly noting the height of the blade tip to the ground as reference. If one end looks higher then other in same spot then you may have a bad shaft,bearing, cracked deck holding spindle. If the blade is lower on one side all the time around the deck, then it probably a bent blade. If that the case- a simple blade replacement is in order. cheapest fix you will ever have. However if it relatd to spindle/deck, then I would pull the deck and inspect it closer. a bad spindle can be replace easily but can be a sticker shock of cost, but well worth the money if tractor is still good shape. If it a cracked deck - I would hammer it back in place and take it to a local garage to have it welded up or have a buddy do it for a case of his favorite drink.

chim · Nov 10, 2012

Could also be someone was careless when sharpening the blade and ground a but too much off one side.

Gary Fowler · Nov 10, 2012

Usually when hitting an object you will bend a blade, but sometimes it is the blade spindle that breaks, sometimes both blade and spindle. If you have an FEL on your tractor, lift the front of the mower up with the FEL by chaining around the front axle. That makes it easy to work on and see what is going on. Rotate the blades and look for uneven or oval movement in the blades. It should be an obvious reason for vibration. Check the blade lengths also, one blade may have broken off the end (highly unlikely but possible). Replacing the spindle wont be a big problem with the mower raised up, just a slight drain on your wallet. Now would also be a good time to replace the blades. If your have used them for 3 years, they are likely getting pretty thin on the end where the blade has a bend to create uplift. That is where mine and my brother in laws wear out. They end up with a split on the end right where it is bent up. He has to replace his about every year. Mine is 2 years old now and in need of replacement due to this problem.
One other thing to check is that the bolts holding the blade on are tight. I found one on brother in laws 5000GT mower that was about to fall off the bolt was so loose. It was cutting the grass uneven which caused me to check his blades for bent blade. One was loose and all were worn out on the end making a V split on the end and razor edge on the top of the lifting edge.

JerryK · Nov 10, 2012

I'd pull the blades and sharpen/re-balance them. The blades build up 'crud' on them... and you might have just knocked too much off one side. Clean them up good before you remove steel to balance them....

Gary Fowler · Nov 10, 2012

Sears blades were 1/3 more than what we found them for at Atwoods Farm and Ranch Supply. Blades looked to be same thickness also. Sears price was $29 each x 3 and we got them at Atwoods for $19 each for a $30 savings.

1fastbob · Nov 10, 2012

I have bent a couple of spindles and the wife even bent a crankshaft on a push mower twice, but I have never bent a blade. Not saying it can't happen, just hasn't happened to me.

chim · Nov 10, 2012

Agri-Supply is a good place to deal with. I get blades from them and the price and quality are very good.

mhampton · Nov 12, 2012

I will check the spindles and replace the blades. Probably a good time to change the oil and filters as well. Based on the condition of the home, maintenance was not the previous owners forte.

mhampton · Mar 25, 2013

Update: Snow started flying back in Nov so this got put off until now. Went ahead and pulled the deck off and gave it a thorough cleaning and visual check. Not any more buildup than I would have expected but it looked like it has never been cleaned. The blades were in pretty bad shape so i pulled them off for replacement. Rotated all the spindles manually with belt and the middle one had a very slight off center spin. Other two looked fine. I will try the new blades and see if the vibration is gone. Also, is there a chance that the belt is stretched and causing the vibration? It took almost no effort to let off the tension bar so my thought is the belt is not very tight.

2458n · Mar 25, 2013

The spindle with,"slight off center spin"will be the problem. Stretched belt will cause slipping not vibration. New blades will help if they were not balanced - but if vibration is still is there after replacing the blades it is time for a new spindle.

mhampton · Mar 25, 2013

That is my thought too. Is the "spindle" the entire assembly? I see in parts diagrams that there is a shaft, mandrel housing, bearing ring, mandrel pull, etc. I am thinking the shaft is what would be bent. I suppose I should just go a head and pull the whole thing a part while I have the deck removed to see if the "spindle?" is in fact bent.

art · Mar 25, 2013

Buy the spindle! Don't go any further! When spinning the other spindles when spinning slow did they spin freely or did there seem to be catches or small lumps or stops?

Look at the sides of the belt for wear, take the belt down to sears and see if they have one there for you to compare the length. Look at the pulleys for belt build up. It doesn't hurt to have a spare driive belt.

mhampton · Mar 25, 2013

They spin pretty freely with no hangups. Also no sign of belt wear on the pulleys. So what exactly is the spindle. I don't see in parts diagram.

2458n · Mar 26, 2013

Spindle will have a pulley on top and a place to attach your blade on the bottom. It will be mounted vertically thru the deck with parts on top of the deck and under. SPINDLE SPINS ON BEARINGS -these may be bad.

mhampton · Mar 27, 2013

Thanks, I kind of assumed that after further research. So now the question is how much should I expect to pay for a spindle? there is a huge difference in price online. I have seen anywhere from $65 for a single spindle without screws and such to $85 for a three pack with all screws included. I don't want to buy junk so any recommendations on where to buy and how much one should be?