Surely my 1980 300TD euro (I think) can't be working at it's best. Each gear change is quite a jolt, my friend mechanic tells me that you should back off just before gear change, even at that it still bangs quite hard. Suggestions?
I don't want to destroy my car. I don't know how many miles she has, original owner claims that the odometer is correct 105K, I doubt it.

I would check the vacuum routing for any leaks. The transmision is controlled by vacuum and any leaks will cause the car to shift hard. There is also an external transmission adjustment that may be done as well. You may want to use the search function on the site and see what others say about the specific adjustment. My car is a 1991 124 with a 602.962 motor so unfortunately I can not tell you the exact routing. If you want to trouble shoot the vacuum leak your self I would suggest getting a copy of the diagram and then buy a hand held vacuum pump. The mity-vac seems to work pretty well and they caost about $35.00 Since there are several components that are controlled by vacuum in the diesel car it may be a good time to buy the manual and the pump as well. Fastlane should be able to get you a CD or if you prefer the paper version, I would suggest Haynes vs. Chilton.

Excellent response, thank you.
I shall check the vacuum system.
CJS