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12/24/10 1:40am - Original Message: 'Tachometer gear'
Former Member
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Houston, TX - USA

1970 454 4 speed A/C power everything else

Joined: 2/7/2008
Posts: 93
I have a new cable in my 1970 tach, but the needle bounces around most of the time and smoothes out here and there but still has a little movement.

Could this be the gear wearing or already worn?  Could this also effect my timing and idle characteristics?

It also makes a ticking noise, that sounds like its in the tach itself.........you can hear it while driving the car.

Fairlane5142010-12-23 22:44:05

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12/24/10 9:05am - Reply: 'Tachometer gear'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

#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: 19511
The tach itself bouncing will have no effect on your ignition timing at all. From the sound of it, the problem is most likely gonna be the tach itself. If you have a reversable drill, you could spin the tach cable with it, and see if the noise is still there, and the needle still jumps. If it does, then your issue is with the tach. If it does not, you prolly need to remove the tach driven gear from the distributor and have a look-see. The fitting on the dist where the cable connects is screwed in, and can be removed. IF the gear there is damaged, chances are high that the dist shaft itself is also damaged...

Joel Adams
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12/24/10 11:40am - Reply: 'Tachometer gear'
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Mounds View, MN - USA

70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe

Joined: 5/24/2007
Posts: 1031
Did you put a little lube on the new cable before you put it in?  There is a chance that it is sticking and jumping.  Otherwise, I completely agree with Joel.


Corvette Specialties is your best source for Corvette parts, accessories and gifts. www.CorvetteSpecialties.com


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12/24/10 12:03pm - Reply: 'Tachometer gear'
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Charlottesville, VA - USA

1978 Silver Anniversary L82 Previously: 1965 300hp Coupe in 1967. 1967 435hp Coupe in 1968-70. 1969 350hp T-top w/ac and all power options.

Joined: 9/3/2010
Posts: 103
I had the same prb in my 69 350, only 15K miles on it and the tach dropped to 0. Replaced the stripped tach gear and it started working, but jumping and then it quit again. It turned out to be the distributor shaft having a broken tooth, so rather than replace the dist I added an electronic tach on the steering column. Then you can set your own redline!


Joe T
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