Thanks for your help and advice. I managed to source a suitable dipstick and obtained a good sample of gearbox fluid which is red and clean, not green! Can anyone tell me please what then are the green drops of oil from the rear of the gearbox (have put white plastic under the vehicle when parked) - about 1-2 drops per week after car use. it's not brake fluid. with car on hoist with mechanic the rear of gearbox housing extension appeared to be moist and it appears that the green drops are cooming from somewhere in this vacinity. he suggests that the red oil is being contaminated by rubbish around the end of the gear box. have obained a litre of genuine mercedes geabox aft (red) just incase i have to add to the transmission. thanks again for your help and advice. regards. ed.