Suzuki DF-6 strange noise at high RPM

[firbdas]

Hello,

I have a Suzuki DF-6 from 2004, it started doing a strange noise at higher RPM, first I thought it was only in neutral but now I noticed that it does it with forward or reverse gear. I attach a link to a video on youtube where we can see and hear the noise it makes.
Meanwhile, I've disassembled the engine and looked at the gearbox and found nothing that could be the cause.
Any one have experienced something similar? Any idea of what might be the cause?

Thanks,

Lourenço

[Hoosmatroos]

Sounds like something is slipping. You say that the gears look oke? What about the clutch? If oke, remove the tail and look at the drive shaft splines. Do you loose drive when the sound appears?
If the sound comes from the gearbox, it could even be the drive shaft where it goes in the pinion gear.