Mine has "barked", if you will, since the day I purchased it new in 2005. Had the transmission upgraded due to the leaking problems these thiings have and it hasen't changed a bit. I was always sounded to me like it's coming from the belt. I figured it sliped a bit when first starting the gearbox and blades...thats a fair amount of mass to get spinning up to the disign speed in a realitivly short amount of time...even if you do engage them slowly. Probably gonna be a mute point for me as it all came to an abrubt halt the other day when I tried to mow a three quater inch steel pin set in concrete. I think I bent one of the spindels just a bit...appears that the greese fitting on top is wobbleing just a smige and I think there may be just a tad more vibration then there was...might be my imagination though...haven't looked at it yet. Opps...got way off topic..sorry. Good luck guys....hope you get your squeal solved!
Chris
Chris