They are known for it.If u can jack up both front wheels and get axle stands under it for safety,then van can be "driven"while u can use a 2" broom handle pressed against one ear and other end pressed against the gbox a various points to trace the rumble.Trust me,this is a remarkably accurate and sensitive test.have assistant "drive"at various speeds and listen.follow the noise.works on wheel bearings ,but be carefull of rotating bits.
caine
August 2008