L4760 making a whining sound (vid)

[DTS62]

My 2 year old L4760 with 577 hours is making a strange whining sound at 1300 rpm's.

https://youtu.be/YuaWTE1Jl1k

This just started yesterday. I was on a job and ran it 4 more hours after first hearing this noise. It always happens at the same rpm and makes no difference if the tractor is moving, or standing still. The steering, 3 point, or fel position have no affect on the sound. It's completely related to engine rpm. Once past that rpm, the noise is gone. All oil and filter changes have been up to date.

Came out this morning and started it up. Same thing.....so it doesn't matter whether the tractor is warmed up or not. I went ahead and drained the hydraulic system and re-filled with Rotella Tractor HD fluid and installed a new 37710 filter. That made no difference. Nothing mechanical seems wrong and everything works as it should.

Do any of you guys have any ideas? I'm hoping to get this solved and repaired on my own as I can't have the tractor down at a dealer for any period of time.

Thanks

 

[Russell King]

Sounds like a relief valve in the hydraulic system so see if moving all lift levers to down position changes it

Makes no sense that the rpm has much to do with that noise but it may be the pump hitting some type of resonance in the system?


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[DTS62]

I had the fel up when I recorded that video, but with the fel and 3 point all the way down, nothing changes. It almost seem like a vibration issue, but I think it's too loud for it to be that.

 

[sheepfarmer]

Sounds like something turning at engine speed is rubbing on something, worse at that rpm, can you look around for a twig or a bent fan blade?

 

[DTS62]

I think I've found the source of the noise. It appears to be coming from the starter motor. I tapped the starter lightly with a hammer while the tractor was running and it temporarily stopped the vibration. I'll pull the starter when I get a chance and have a look. I'm thinking the gear isn't retracting all the way. I'll put some lube on it and see what happens.

Thanks to you guys for responding with the suggestions.