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