I was driving a Range Rover with 4BD1 engine, and it started to shudder and shake the steering wheel so bad that I didn't think I could hold onto the wheel and keep the vehicle on the road, would of been doing 95-100 kph, I pulled up, had a look underneath the vehicle, couldn't see any thing amiss, resumed my journey, didn't happen again. However, after talking with a friend, who had had the same thing happen in a 110 county, with 4bd1, we found that the panhard rod bushes were buggered. Why it did it only once I still have no idea. The bushes, when removed were very soft and the rubber was all broken and cracked. Replaced them, didn't happen again.