1979 speedo not right

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Apr 7, 2013 | 07:31 PM

Corvette_Summer

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1979 speedo not right

My speedometer is not right, it bounces a little at start but then it settles out, but even then it's wrong. Sometimes I'm going 55 and it reads 20, and other times I'm going 30 and it reads 60! It's never right. I've got the cruise control box and I've cleaned and lubricated the cables. From here I'm not sure what to do.

If its the cruise box, is there a way to fix it, or do I just have to buy a new one?

Apr 7, 2013 | 07:43 PM

calwldlife

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Joined: Jan 2007

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From: Southern Cal Ca

St. Jude Donor '22

Quote:

Originally Posted by Corvette_Summer

some members have found a longer cable at the parts store and bypass the cruise box.
this will tell you if it is the speedo or the gears in the transducer.

Apr 7, 2013 | 07:57 PM

calwldlife

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From: Southern Cal Ca

St. Jude Donor '22

I think I would hook a power drill up to the
cable from the speedo and see what is up.

Apr 7, 2013 | 08:55 PM

Billem

Racer

Joined: Nov 2011

Posts: 374

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From: Charleston SC

Quote:

Originally Posted by calwldlife

I think I would hook a power drill up to the
cable from the speedo and see what is up.

I'm not positive about a cruise-control, but when doing the drill thing without CC, REVERSE!! Have a great day, Bill

Apr 7, 2013 | 09:18 PM

couperdecar

Burning Brakes

Joined: Feb 2006

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From: Regina Saskatchewan

I replaced the upper , then the lower. Still had the same problem. I installed the longer one and speedo stopped bouncing.

Apr 7, 2013 | 09:33 PM

cagotzmann

Melting Slicks

Joined: Jun 2011

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Quote:

Originally Posted by Corvette_Summer

Cruise control box has 2 disc's that can stick which causes the cable to jump. My 78 worked after I cleaned the Cruise control unit. Now the 2 discs were worn and I replaced the unit after about 3 years after cleaning. I would try cleaning first. It was difficult to get the cruise control to work well after the cleaning. It was hard to reassemble and adjust to hold the speed properly, but the speedo at least worked.

Oct 27, 2013 | 05:49 PM

stealth799

6th Gear

Joined: Sep 2009

Posts: 6

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From: Clinton Utah

Bouncing Speedometer

I have the same problem with my speedometer and had the speedometer head rebuilt by corvette clocks by Rodger once I got it back installed it had no problems for about a year then all of a sudden started to act up jumping all over the place. Took the cable out and inspected it for any burn marks none noted sent the speedometer back to Corvette clocks they tested it out putting the head through all kinds of tests they could not duplicate the bouncing issue and returned it back to me. I greased up the cable and re installed the speedometer and all worked fine until about a week ago and the problem came back bouncing. Now my 79 does not have cruise control installed guess that was an option back then it is an early model if there is a cruise control box where would it be located? I also installed a new turbo 750 R transmission from performance transmission a few years back. Any suggestions out the would be much appreciated.

Thanks

George