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hi
wath can it be . the speedo or cable or ?
when i start driving up to 30 miles the speedo works fine and then it makes a hell of a noice and it gos right up over a 110 miles . but only the speedo not the car

Both could cause the problem.

Unscrew the cable housing from the back of speedometer and carefully pull cable out of the housing. It should come out from the top but there is a remote chance cable might have fit in the housing reversed. It will be very greasy and dirty so be careful it doesn't hit any upholstery if you pull it out.

Clean the old lube off and carefully check for any kinks or broken strands. One way some have checked for kinks is by holding it in the middle. Let ends fall to the sides and look and see if any bends are evident then roll the cable between your fingers. The cable ends hanging down should turn and move very smoothly with no jerking at the ends. If that is good, then put some new speedometer cable lube on the first two thirds of cable and insert it back in the housing. Also make sure there are no sharp bends anywhere in the housing going to transmission.

If there is a kink then you can replace the cable only. American parts stores have universal cables you can cut to size and put a new end on. I don't know if anything that would fit is available in Germany.

The speedometer has an oil hole hidden under the screw or nearby as shown in the bright square in the picture. Put a drop or two of oil in the hole and rotate the brass end (where the cable slides in) with your finger to work the oil in a little bit. It should turn very easily. If the speedometer has never been touched in 60 years, that drive shaft, the gears and worm drive inside could also have some very dry and hard grease. You might need to take it out and clean and lube the gear train which will be somewhat like the one in a later speedometer as shown in second picture

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Thanks Howard, I have a brand new speedo for "Black Diamond' and I want to lube it now while it's in the box. I use an oil called liquid bearings - 100% synthetic.

ok . great thanks for the info

What about if my speedo just jumps back and forward from 0-110 or whatever no matter the speed as long as I'm moving. It goes crazy
Thanks guys always a pleasure
-Garrett

Same applies. Those are two speedometers out of early 50's.

The second picture shows the U shaped magnet on the side of the round cup. Those do not touch but rather the magnet smoothly spins around and induces a field which the cup tries to follow. Anything such as a dry or kinked cable or dry bearing that hangs and then breaks free and allows the cable to whip so the magnet can suddenly spin rapidly, the cup will try to follow -- hence the jumping.

Best to take care of it now. If it gets too bad, the needle can jump so violently it hits the stops and either breaks or falls off or the hair spring jumps, gets twisted and damaged. Several have had that happen to theirs in the last couple of years.

the physics of the speedometer are fun ,one cant completely magnetize aluminum ,so the faster the magnitized iron ring spins ,which is attached to the cable ,the more of a magnetic field it makes ,and the more it partially magnetizes the outer aluminum ring and so it tries to follow the spinning iron ring and its attached in some way to the needle my speedometer staqrts to wobble at 60 miles per hour