The gears in those speedometers are designed to be accurate with a particular transmission sending unit. Unless you have one which is designed for the transmission in your car it is going to be a waste of time to try any repairs.

I seem to remember that green wire being the one which connects the speedometer and the sending unit on the transmission. I have no idea how or why you would try to get that speedometer working since any information it shows will be inaccurate, either the speed or the mileage.

I believe the FSM says if your engine oil pressure is 1.7 bars when warm at idle it's OK. The oil pressure should go to immediately to 3.0 bars when you push the accelerator.

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84 300SD
85 380SE
83 528e
95 318ic