The pilot bearing would normally be turning with the input shaft when the clutch is engaged would it not? I would think that you would be more inclined to hear it when the clutch is disengaged and the clutch is spinning around the stationary input shaft.
Does that sound correct?
Yes, that sounds correct to me on the pilot bearing. I believe a bad pilot bearing/bushing would make a sound oppositely to what you are hearing. I've been thinking about the grumble and trying to come up with anything that it could be EXCEPT a bearing somewhere along in the transmission along the input shaft..... and not coming up with much.
Check me on my understanding - the noise exists when the clutch is engaged and the transmission is in neutral so that the input shaft is turning. The noise is a low grumbling sound, and it goes away or changes when you step on the pedal to disengage the clutch. Is that correct?
And I'm guessing that the noise actually decreases when you put it in gear and drive off. Is that so? 2wd vs 4wd?
I am assuming that you have enough free play in the clutch system so that the throw-out bearing isn't touching the pressure plate when the clutch is engaged. That's worth checking. As a test, you could pull backwards on the lever that works the throw out bearing just to make sure it has clearance from the pressure plate.
Another check is to look at the oil or cut open the hydraulic oil filter. You may see particles or silvery metal flakes if it is a bearing.
It may also be possible to take off the shifter cover and peer around inside. Not sure if you can on that transmission, but if you can it is easy and always a chance of learning something. Do not run it with the cover off. The shift collars not only shift the gears, they keep the gears from moving freely and shifting themselves.
Once or twice in my mechanical career I've been lead astray by thinking I had a bad bearing when what was actually happening was that a piece of metal had gotten bent or somehow leaning on the engine/transmission case and was vibrating so that it sounded like a bearing. Rare, but it has happened to me so worth a look.
If those tests don't help, then infortunately it does sound like a transmission bearing. It may not be the tranny input bearing; it could be a bearing anywhere along that input shaft. Some transmissions are made in two pieces that slide together with a bearing isolating the front and rear halves. I am not sure what the Kubota tranny looks like, but all manual transmissions are similar.
best of luck,
I think that's a great tractor with a great transmission. Sorry for the problems, but worth fixing.
rScotty
it does sound like that's where it is coming from.
