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Topic: speedo working intermittently

in Forum: C3 Interior


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speedo working intermittently (1/7)
 3/6/15 4:08am
daveo76
Former Member

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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.


Joined: 8/25/2005
Posts: 857

My speedo is working only intermittently.  Cold mornings seem to be the worst.  When it's not working there's a noise coming from the transmission tunnel - presumably it's the cable's attachment at the tranny.  Any thoughts?  I would think if something was physically broken down there the speedo would never work, not intermittently work.  I've not had a chance to put it up in the air to take a look - maybe it will be obvious once I do so?  

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1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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Re: speedo working intermittently (2/7)
 3/6/15 9:45am
my7t1Lifetime Member
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Dorr, MI - USA

Vette(s):
71 Colonnade Hardtop Coupe Torch Red with black interior originally L48 built to push around 360hp


Joined: 8/21/2002
Posts: 2581

I had the same intermittent problem with mine. The cable was worn on the ends. Replaced it and it works fine. Not too bad of a job. "T"

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Re: speedo working intermittently (3/7)
 3/6/15 11:08pm
dwright
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Victor, NY - USA

Vette(s):
2004 Commemorative Edition Coupe, Auto w/HUD. 13K miles in 2015. Sold 1982 Red Coupe


Joined: 7/12/2004
Posts: 6836

They need to be relubed regularly. Disconnect at the tranny, remove the inner cable, use special lube, slide it back in.
If the end is twisted, you will need to replace the cable. If you have cruise control, the lower cable is not too difficult. If not, the connection behind the dash is tricky, but can be done. Don't hurt your back.


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Re: speedo working intermittently (4/7)
 3/9/15 2:15am
daveo76
Former Member

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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.


Joined: 8/25/2005
Posts: 857

Thanks guys.  No CC in '76 so my cable is one piece.  I replaced it when I did the engine a few years ago - probably not much more than 1K miles on it.  So I'm concerned it's more of an installation problem than a wear problem.  I think I'm just gonna have to get it up in the air so I can figure what's going on.  I got tangled up doing a rear brake job on my suburban (drums, ugh) this weekend so I ran out of time.  Will keep you posted...

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1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Re: speedo working intermittently (5/7)
 3/9/15 12:51pm
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: 20129

daveo76 said: So I'm concerned it's more of an installation problem than a wear problem.

Yer prolly on the right track with that idea. If the ferrel for the cable is loose where it connects to the speedo adapter, OR the speedo adapter itself is loose, it can cause those exact issues...noise, and erratic speedo. Being a 4 sped car, it should have the 90deg adapter/ratio corrector on it right out of the trans, and the cable attaches to the adapter. Yer gunna hafta crawl under there and have a look....Ouch



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Joel Adams
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Re: speedo working intermittently (6/7)
 3/10/15 1:27am
daveo76
Former Member

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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.


Joined: 8/25/2005
Posts: 857

Thanks, Joel.  Yep, gotta do an oil change anyway so it'll be up on the ramps or jack stands in the near future and I'll check it out.  'cept now you have me worried - I'm not sure I remember there being a 90 degree adapter on the tranny for it.  If not, maybe that's my problem.  

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1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
Re: speedo working intermittently (7/7)
 3/10/15 10:45pm
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: 20129

It will look like dis un, if ya has it. MOST 4 speeds used the adapter, but it might depends on what rear end ratio the car has.



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Joel Adams
C3VR Lifetime Member #56    

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(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

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