Speedo??
Thread Starter
Heel & Toe
Joined: Sep 2017
Posts: 15
Likes: 0
Speedo??
Just bought a 1978 c3 and the Speedo doesn't work, at all. I realize there is a cable that comes from the back of the Speedo and follows down to the tranny and connects to a hard plastic gear, I guess my question is, how do I know what to replace?? In addition, if anyone has a diagram to the vacuum lines for headlights that would be awesome. Mine turn on but dont come up. Thanks in advance.
Race Director
Joined: May 2006
Posts: 18,648
Likes: 2,557
disconnect the cable at the trani and use an electric drill in reverse to spin the cable while checking the speedometer.
if the gauge moves continue with pulling out the plastic gear and check the teeth.
this link is for the vacuum diagrams
http://repairs.willcoxcorvette.com/w...schematics.pdf
if the gauge moves continue with pulling out the plastic gear and check the teeth.
this link is for the vacuum diagrams
http://repairs.willcoxcorvette.com/w...schematics.pdf
Melting Slicks
Joined: Apr 2006
Posts: 2,202
Likes: 64
From: Bocabec, New Brunswick
With cruise control there are 2 cables, one from the transmission to the cruise control box and one from the box to the speedometer. If the control box is missing then whoever removed it probably didn't replace the 2 cables with the longer non-cruise single cable directly from the transmission to the speedometer.
Burning Brakes
Joined: Jul 2017
Posts: 1,113
Likes: 149
From: Frisco TX
With cruise control there are 2 cables, one from the transmission to the cruise control box and one from the box to the speedometer. If the control box is missing then whoever removed it probably didn't replace the 2 cables with the longer non-cruise single cable directly from the transmission to the speedometer.
I just replaced my cruise module and now the speedo works fine.
Last edited by LenWoodruff; Sep 15, 2017 at 07:57 AM.
