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72 tach cable

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Old Apr 7, 2010 | 07:30 PM
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Default 72 tach cable

My 72 tach quit tonite and when I unhooked it an inch and a half of the center cable stayed it ht e distributer. What kind of a job is it to change the cable and the outer sheath is not that greagt either!
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Old Apr 7, 2010 | 08:26 PM
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Not as bad as I thought it would be. I took out the driver's seat so I could lay on the floor with my head under the dash. There's a clip on the tach-end of the cable, you just push the clip toward the tach while you pull the cable and it'll release.

It would've been easier if I had someone help me that could have pulled the cable from the engine compartment.
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Old Apr 7, 2010 | 08:56 PM
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thanks that gives me a start
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Old Apr 8, 2010 | 07:26 AM
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Does anyone have pics?
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Old Apr 8, 2010 | 07:39 AM
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You'd have to have an endoscope to get pix of that....... It's easier than you think to remove the cable from the cluster....Just do what the guy above said. There's a step by step posted here somewhere...Do a search of removing the instrument cluster or something like that...

Last edited by jeff79'; Apr 8, 2010 at 07:45 AM.
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Old Apr 8, 2010 | 02:08 PM
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Thanks for the help!
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Old Apr 8, 2010 | 04:45 PM
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Taking out the seats as Brooklinite said is the best tip. You should be able to push the clip in with a long screwdriver.



View from under the dash:



Have a helper push in on the cable, from the engine compartment until you press in the tab, then pull it out. Good luck.
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Old Apr 8, 2010 | 07:21 PM
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Thanks for the pics now I see what i'm dealing with!
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Old Apr 8, 2010 | 08:39 PM
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In addition to fixing the symptom of the problem (broken cable), you should also consider fixing the cause of the problem: On C3 Corvettes, the tach cable has to make a near-90-degree bend coming out of the distributor to avoid hitting the firewall. This sharp bend in the cable causes the cable to break prematurely.

There are 90-degree adapters available from aftermarket sources, but these cause worse problems: If you install a 90-degree adapter to straighten the cable, the additional torque required to turn the adapter gears will cause additional thrust loads on the distributor crossgear, pushing the gear hard into the wall of the distributor housing, damaging the housing, and causing the crossgear to seize with resulting destruction of the mainshaft and crossgear.

Rather, you should follow the GM Service Bulletin that was issued to fix this problem. This SB instructs you to re-orient C3 distributors, re-clocking the distributor about 45 degrees clockwise. This gives the tach cable a straight shot at the firewall penetration, giving you "everlasting" cable life.

For a copy of this SB and instructions on distributor installation, complete with photos, drop me an e-mail request for my "How to Install Your Chevy Distributor" paper:

V8FastCars@msn.com

Lars
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Old Apr 8, 2010 | 08:46 PM
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Originally Posted by lars
In addition to fixing the symptom of the problem (broken cable), you should also consider fixing the cause of the problem: On C3 Corvettes, the tach cable has to make a near-90-degree bend coming out of the distributor to avoid hitting the firewall. This sharp bend in the cable causes the cable to break prematurely.

There are 90-degree adapters available from aftermarket sources, but these cause worse problems: If you install a 90-degree adapter to straighten the cable, the additional torque required to turn the adapter gears will cause additional thrust loads on the distributor crossgear, pushing the gear hard into the wall of the distributor housing, damaging the housing, and causing the crossgear to seize with resulting destruction of the mainshaft and crossgear.

Rather, you should follow the GM Service Bulletin that was issued to fix this problem. This SB instructs you to re-orient C3 distributors, re-clocking the distributor about 45 degrees clockwise. This gives the tach cable a straight shot at the firewall penetration, giving you "everlasting" cable life.

For a copy of this SB and instructions on distributor installation, complete with photos, drop me an e-mail request for my "How to Install Your Chevy Distributor" paper:

V8FastCars@msn.com

Lars
Very interesting....I may look at that...
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Old Apr 12, 2010 | 07:18 PM
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Just to report usualy everything I touch on this car turns into a PITA project but for some strange reason after getting the cable today and with my son helping me I had the tach cable changed in about 15 minutes! Never even took the seat out just removed the gromet and stuck my hand in till I felt the clip while my son pulled and out it came. As he fed the new cable I lined it up by feel and it went right on!! Also Lars I guess I got lucky as I adjusted the distributer when I did the engine so the tach cable has a lazy "S" bend in it and the vac can is behind the wire loom istead of in front. I guess I coud have gone one more tooth and took out the "S" but I thought I was doing something GM didn't do.
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