I own a Landrover Discovery 200 TDI, its a 1993 model and for its age is in good nick. Over the last few months a problem has developed which has me and the mechanic that does the maintainence stumped. At first we thought it was the near side CV joint but he replaced it and the problem is still there. Basically its when im driving really slow as when in a que of cars, the noise begins with a clunk as i disengage the clutch and then continues until i re-engage the clutch. The vision I get is of two big cogs not meshing correctly. When i drive at speed there is no sign of the noise. Also it doesn't happen every time i drive slow, which has made it even harder to diagnose. Any ideas?