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Bouncing speedometer (1/8)
 11/30/19 12:03pm
Vette78RLGold Member
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1978 Silver Anniversary. Restored in 2012. All new 'complete' suspension f & r, engine, trans, exhaust, interior. Car is driven - garage kept but not a trailer queen.


Joined: 10/21/2013
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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.  

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Re: Bouncing speedometer (2/8)
 11/30/19 1:19pm
manchestersharkLifetime Member
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Equinunk, PA - USA

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1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.


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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.  

Re: Bouncing speedometer (3/8)
 12/1/19 2:36am
73shark
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Overland Park, KS - USA

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1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


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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. 



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Re: Bouncing speedometer (4/8)
 12/1/19 9:51am
manchestersharkLifetime Member
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Equinunk, PA - USA

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1972 conv, 4-speed, 350, 200hp, numbers match, rally wheels, war bonnett yellow w/white top. good condition, nice driver.


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Posts: 2001

WINTER!!!!!!

Re: Bouncing speedometer (5/8)
 12/1/19 10:08am
Adams' AppleLifetime Member
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Duncanville, TX - USA

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#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
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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.



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Re: Bouncing speedometer (6/8)
 12/1/19 10:13am
Vette78RLGold Member
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1978 Silver Anniversary. Restored in 2012. All new 'complete' suspension f & r, engine, trans, exhaust, interior. Car is driven - garage kept but not a trailer queen.


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Posts: 3

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!

Re: Bouncing speedometer (7/8)
 12/1/19 10:40am
Vette78RLGold Member
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Vette(s):
1978 Silver Anniversary. Restored in 2012. All new 'complete' suspension f & r, engine, trans, exhaust, interior. Car is driven - garage kept but not a trailer queen.


Joined: 10/21/2013
Posts: 3

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. 

Re: Bouncing speedometer (8/8)
 12/1/19 9:18pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19674

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?



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Joel Adams
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(click for Texas-sized view!)
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"