The cable can be pulled out of the housing(jacket) and cleaned and oiled. I had a terrible squeal from my speedo when cold, it wasn't the cable causing the noise, it was the bushing in the speedo where the cable nut threads on.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy