noise from mower gearbox

[IKE76]

I had a bearing go bad in my Kubota 60" mid mount mower gearbox. I replaced all the bearings since I had it apart and it sounds great when I run it.That is until I lower the deck. Then it sounds horrible. Worse than it did when it had the bad bearing in it. As soon as I raise the deck back up it sounds fine again. I took it all apart and rebuilt it again just in case I might have done something wrong. Same thing. Any ideas ?

 

[bellweather]

I assume the PTO is engaged when it's raised and quiet? and it starts making noise when the deck is lowered while leaving the PTO engaged?
is it a full RPM?

 

[dougtrr2]

I would look at the PTO shaft bearings. With the ignition key in your pocket you could put the PTO in neutral and then turn the blades by hand to see it you can hear, see, or feel anything out of the ordinary. Try it with the mower up first and then lower it and see if your can tell what is going on. Good luck.

Doug in SW IA

 

[ruffdog]

Are the splines lubed so the pto shaft can extend?

 

[IKE76]

When the deck is engaged it is quiet when it is in the raised position. It gets noisy when lowered.
Everything was greased while I had it apart so I don't think that's the issue. You start hearing the noise get more pronounced as you go past half throttle.
I'll try moving the blades by hand this weekend.
Thanks everyone. This one has me stumped.

 

[SPYDERLK]

There may be some damage to a gear, but I cant see why this would change sound much from raising and lowering - and under no load to boot. ... I second the ? full rpm? question.
larry

 

[walter boatwright]

There may be some damage to a gear, but I cant see why this would change sound much from raising and lowering - and under no load to boot. ... I second the ? full rpm? question.
larry

Take the mower deck off . The drive shaft off ,and see if the input shaft is loose. Check the fluid in the gear box.and if all looks fine . Take the gearbox off and check for any thing loose at the output shaft .Start checking the drive shaft. If there is a high pitch squeal its most likely a U-joint. Also check the idler pulleys for tightness.

 

[IKE76]

The gears were in very good condition. Barely any signs of wear. Both input and output shafts were tight. I put new gear oil in it before trying it also. The noise is not high pitched at all. It is more like the growl you might here from something being shaken or out of balance. The u-joints seem fine also. The noise starts at about half throttle. The faster you go the worse it gets. Idler pulleys feel ok when I spin them. Not loose or super tight.
However when the deck is in the raised position it doesn't matter how fast you go. It never makes any noise.
If the problem was with one of the shafts or the u-joint, I would think that it would have been evident before I put the new bearings in.

 

[boomer1025]

Sounds like something changed the working angle of the pto shaft. Is the input shaft on the gear box tight, no up or down play, how bout in or out movement. Didn't miss a spacer on the input shaft or output shaft ? Gears meshing properly. Something causing the gears to load up/backlash not set properly causing the noise.

 

[whis]

if you had the drive shaft apart you my have the u joints out of time

 

[Kanook]

if you had the drive shaft apart you my have the u joints out of time

I was thinking the same thing. Sounds like it may be the relationship between the u-joints at both ends. They should be at 90 degrees to one another....not aligned....I made that mistake on a pick-up truck driveshaft a long time ago.

 

[SPYDERLK]

I was thinking the same thing. Sounds like it may be the relationship between the u-joints at both ends. They should be at 90 degrees to one another....not aligned....I made that mistake on a pick-up truck driveshaft a long time ago.

AFAIK this cant happen on KUBs. The telescoping spline is "keyed" ... on the BX series anyway. :confused3:

 

[zzvyb6]

if you had the drive shaft apart you my have the u joints out of time

Folks I believe we have a winner ! The noise and vibration from the mower deck in a lowered position (but not in some other one) means the input and output shafts aren't parallel OR that the PTO drive shaft is out of phase. If it's put together properly, the inner cross yokes must face the same (as in no angle between them). Otherwise you will get a cyclic wobble that will rattle your nerves and your bearings.

Had this happen to me once a while ago. Was asked to help chop some corn. Jumped on the 4430 with the chopper and a chopper box in tow and drove down to the field. Things went well until I made my first right turn. Midway through, a 1000 rpm, pto shaft went flying by my head. Knocked my cap and glasses off. Broke all the glass out of the cab and smashed the twoway radio. I believe the farmer's son put the shaft together 90 out of phase. Making the turn wobbled the shaft and caused it to break and go flying.

Had to find my glasses before I could read how to turn off the tractor. We had to search the field with a metal detector in case the next crop would feed steel to the cows. -- just a little side note....

 

[Toolguy]

What year is your mower? The shaft on my 2005 60" mmm is keyed. It only goes together one way. If yours is an older model it may not have the key and could be out of phase. If the shaft has one wide spline on the male side then it is keyed and should not be the cause of your problem. It sure sounds like the shaft is the problem, though. Good luck.

 

[Toolguy]

I just went out and checked and both my mmm and brush hog shafts have the yokes aligned, not 90 degrees to each other. Yours should be too, regardless if it is keyed, or not.

 

[Kanook]

My Bad.....In my previous in put I should have said 180 degrees....been out of high school for 50 years.

 

[IKE76]

Thanks for the picture Kanook. I really didn't understand what you guys meant by out of phase or time. It's said that confession is good for the soul.........I was kinda thinkin some of you guys are nuts. I'm 56 years old and been driving tractors on a farm for 30 years. I've never heard those terms being used in reference to a u-joint or pto shaft. Now I get it. I just went out to the garage to look at the shaft. It's splined but not keyed......and it's off about 35-40 degrees. I took it apart and lined them up right. I will put the mower back on the tractor tomorrow and try it.
I'll let you all know what happens. Thanks to all of you for taking the time to offer help.

 

[whis]

that was your problem

 

[Coyote machine]

For future reference always mark things like drive shafts so you can make sure they go together exactly as they came apart. Things that go round at high speed and adjustable angles don't like to be out of balance.
Etch, mark, or use tape and marker to help identify, then take pics to show further how parts line up, or the step by step disassembly process. That way if time passes you have several ways to reference your work.:thumbsup:

 

[IKE76]

Thank you to everyone who responded to my problem. It was the shaft misaligned. I'm surprised that the shaft is not keyed. The ones on my tiller and bush hog will only go together one way and I just assumed this one was the same way.