Speedo Cable

‘75 w/304. Heard a “ping” and my Speedo went nuts. i.e. showing 30mph at a stop, then 10mph driving 45. Pulled the end from the tranny and noticed there is about 3/4” of play within the cable; I can move the cable in and out of the sheath. It seems to me there is no way it’s going to stay connected. Thoughts?

 

Did the end break off? Remove the cable, pull out the core and inspect it. If the core is broken, you can replace it.
https://www.amazon.com/speedometer-cable-repair-kit/s?k=speedometer+cable+repair+kit

 

No breaks. I can spin it manually and the speedo works, just seems as though there is too much room for movement

 

Humm, maybe as timgr said broken inner cable. just a thought, would the speedo read 30 mph at when stopped? Seems like it would fall to 0 when the cable stops turning should it be broken. Kinda makes me think the problem is within the speedometer it's self. I have an old broken speedometer in my junk box that is hung up on 50 mph. with no cable attached.

 

A mechanical speedometer is delicate, and turns on jewels like a watch. There is a big coil spring, like a watch spring, that returns the needle to zero. If the needle does not return to zero, that suggests something stuck in the works.

The 3/4" of end play is ok if the ends stay engaged with the drive gear and speedometer head, when you slide the core to the end in each direction.

 

The brevity of my post is misleading. The speedo had worked find, albeit a bit “jumpy”, before this happened. Performance varies now between reading a speed when stopped, to incorrect speed, to working fine. All within a few blocks. I’m wondering if there is a mechanism which is supposed to keep the inner cable from moving in and out, and maybe that has failed

 

The end play gets reduced to about 1/8” at its smallest point

 

I agree, the inner cable should simply slide right out for inspection. if it appears not broken or frayed I would bet the problem is inside the speedo it's self. I did have a speedometer that would jump around when driving but would return to 0 when stopped. All it needed was a good lube to the lower 90 percent of the cable to fix the problem.

 

No mechanism. The length of the cable should be slightly shorter than the sheath. Not a precise quantity; short enough so it doesn't bind, long enough so it stays engaged at each end.

 

Ah, ok. So, I COULD just slide it out, lube, and return it?

 

Definitely.

 

Thanks, appreciate the advice

 

I think you should not lube the top few inches of the inner cable so to prevent lube from working into the speedometer it's self. Also there is a special lube for these cables available at the flaps if you so desire.

 

Funny, I was just about to ask that. The cable looks good, slid right out. The speedo end has a collar, so, pulled from there. Not wishing to do the right thing, I think I’ll just clean it, and lightly dry lube it

 

Graphite grease used to be the thing.

If you really have a lot of end-play, is it possible the outer sheath has become damaged and
"stretched?"

 

Not sure what kind of lube the special cable lube is, it maybe a dry graphite or a grease of some kind. But I simply used some CV joint grease to lightly coat mine, it worked well.

 

Possible I imagine, although it looks good to me

 

I’ll do that

 

Ah, that is correct, I had brush damage mine once, the outer casing was made from a twisted looking material, it simply stretched and unplugged the inner cable.

 

So, that didn’t work. It’s acting more smooth, but that’s it. Odometer is working. PO replaced it some time ago and it has only 2600 miles on it, so, I’m going to take a look at it. Is there anything I can look for