my dad drives an 02 reg vauxhall astra 1.8 sxi, but as you drive a long the road is a sort of rumbling noise like: dum...dum...dum. sort of thing. i can also feel it vibrating through the floor. it doesnt do it all of the time though. no one can seem to tell where its coming from. my dad has also had the front wheels of to check the bearings but its not them.
does anyone have any ideas on what it could be? or has anyone ever had this problem before???
thanks in advance