My guess would be the cable too so just try lubing it before you condemn the speedometer itself.

I don't remember if the W123 is a PITA to remove the speedo from the cluster or not or if you would have to send out the entire cluster for service...maybe others can tell you if this is feasible.

If you can't easily remove the speedo from the cluster then your oil pressure line will be open and you'll need to cap the oil pressure line if you want to be able to start the car with the cluster removed...otherwise oil will be pumped out of the line.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz