Help! Speedometer just stopped working in my 79 L48

[Rmagid]

As I was driving on the freeway today I saw my speedometer go from 65 to below zero immediately. I can now hear a spinning noise that kinda clicks at the speed that I'm driving at. I was wondering if my speedometer is shot or if it's the cables. I have cruise control but it hasn't worked since I got the car. The tach also does not function properly and it wildly flys all over the place. I checked and the speedo wires are still connected to the back of the speedometer. Any advise would be appreciated.

Thanks,
Ryan

 

[6880 Mike]

Check the cables first. They get old and can break.

 

[Rmagid]

Thanks Mike. I guess I can try that first. The tach is still doing it's random numbers thing and does that have anything to do with the speedometer cable? I wasn't sure if it got any info from that or not.

 

[JohnZ]

Thanks Mike. I guess I can try that first. The tach is still doing it's random numbers thing and does that have anything to do with the speedometer cable? I wasn't sure if it got any info from that or not.

Nope. The speedo is mechanical (driven by a cable from the transmission, through the Cruise Control transducer, to the speedo head), and the tach is electronic, driven by a signal from the distributor, through the tach filter, to the tachometer.

 

[Rmagid]

Thanks. Speedometer works again and just ordered a new circuit board for the tach. Hopefully that will fix that issue.