i have the same prob with my 2000 zj quadradrive, i've been driving it for a month like this now and it hasn't got any worse. will it get worse??
i took it to a few mechanics they said its the diff. one told me he wants to replace the whole thing, is that a good idea? i'd rather keep it as original as i can as i don't trust a rebuilt diff, cuz it mite happen again soon...
the noise mine makes starts as 30 km/hr like yours and it whines and as i get up to about 60 km/hr, the whining sorta rattles, and as i let go of the gas and decrease in speed, the whining sounds like its winding down as opposed to how its winding up as i go past 30...maybe someone can diagnose from that if my case is cracked or its just something inside the case?