Has anyone had an issue with the speedometer needle 'bouncing'?  Occasionally, it will register correctly then proceed to bounce from 0 to 110 back & forth.  Have been having to use tach rpm to have an idea of current speed.  After reading some of the 'speedo cable replacement' entries in this forum, I think it may be more cable related than trans-gear related since it does work part of the time.  Car has cruise control,  which will set, but freaks out with the speedo bouncing.  Anyone?  Thanks for any replies.  

Hi, I would try the easy stuff first. Pull the cable and lube with silicone or graphite grease.  OR, see if cable had broken strands of wire, which may be hanging up in the housing.  

You can get speedometer cable lube which is basically graphite and a thin liquid. I wouldn't use a grease because it gets stiff in the winter and can cause problems. 

WINTER!!!!!!

By all means check/lube both cables first. If that doesn't correct the issue, your problem is most likely the Cruise Control Transducer. It also has a set of gears & grease inside that gums up and turns hard over the years. If you catch it in time, it can be repaired/lubed, but if not, it must be replaced. Once it locks up, it will twist the lower speedo cable off.

Thanks much to both '73shark' & 'manchestershark' for replying!  I will try the bottom cable 1st using speedometer cable lube (Amazon comes thru again - just ordered a tube!).  I'll repost after I get the opportunity to work on it.  And yes, Winter is indeed upon us.  Fortunately, we don't get much snow so can drive it pretty much year-round.  Thanks again for the tips!

And thanks "'Adams' apple" for his reply. 

I've wondered about the transducer also but since it kinda of 'sets', I figured it was more cable related however....  since it's the original transducer which is now a ripe 41 years old, it may be a combination of all.  Rebuilt transducers are hard to come by  after a interweb search.  Found an entry on Ebay out of Ft. Worth for either rebuild ($191) or new ($199).  Gee, let's see...... ahh duh!  Less than 10 bucks for a new one? Just not sure about Ebay.  Never know whether to try sellers or not. Can only go by reputation stats.  This one is 98.5% reliable over 8,500+ customers so probably trustworthy enough.  Will still try the cable lube route 1st but as 'Adams apple' says, eventually the TD will go belly-up anyway.  Thanks to all again. 

You can open the transducer up yourself for a look-see, and get an eye on the gearset. I've lubed MANY of those turds over the years.

bwt...does the speedometer make any noise while it is acting up?

Reply to 'Adams Apple' post:   No, speedo makes no noise.  If on a level straight road and hold constant rpm, the speedo works fairly well.  Just a bit of movement around the current speed.  If speed up for example, needle goes crazy and bounces back and forth but eventually, for the most part,  settles back down.  But any speedup/slowdown/ whatever makes it wacko again. 

Got the lube from Amazon but have not had anytime to work on it yet.  Has been cold and rainy here and need to have it out of the garage to raise it up to get under it.  As mentioned, once I have a chance to actually accomplish the work, I'll repost with how it turned out.  Thanks again to all who have posted.   

I have a 78 Pace Car, 4-speed/L82. No cruise control and my speedometer bounces until I get above about 30mph then it smooths out. As the speedo drops below 30 upon deceleration it starts bouncing again. I replaced the cable and got no love.  I think the issue is in the speedometer itself, maybe dirt, I don't know yet?