R129 strange transmission noise

[jjrodger]

I noticed a strange noise from the transmission today. It is very difficult to descrive but I will give it a go.

The noise occurs when pulling away from a stop. It occurs at approximately 10mph. It is like a graunching, grinding, rumble of a noise. It lasts about one second. I'm sure I can also feel it. It seems to come from the left hand rear side of the car (left hand when sitting in it).

What could it be? Differential? Transmission? The car has 70k miles on it. The transmission fluid was changed about 1 month ago. Makes no difference whether the car is cold or hot.

Please help!