At 1500 revs and on the move, my mates 2003 Td6 feels like it is going over some rumble strips. Cant feel it at any other revs, nor does it transmit up the steering column . Increasing speed stops it. Indie LR suggested loose chain in transfer box . It had an egr code on it which he cleared. Any one experienced any thing similar ?

had the same thing on an ML merc , was an engine mount failed , engine was resting on the chassis but only vibration was around 1700 revs