Lets talk Speedometer
Thread Starter
Team Owner
Joined: Mar 2002
Posts: 44,626
Likes: 1,826
From: Huntsville AL
Lets talk Speedometer
I just completed a complete interior overhaul and took the car for a spin. When I first picked up this 77 a couple mounts ago I only drove it a couple of times before I started the interior upgrade. Can't say fro sure if the speedometer was working correctly at that point. It is a 77 without cruise control.
When I'm shifting 1st, 2nd, 3rd and there is torque the speedometer reads zero. Let off the gas to shift and it jumps up to 40 MPH or so. In other words when I shift from say 2nd to 3rd it goes from zero to 40 and back to zero. After I'm in 4th gear it reads 40 - 50 MPH MAX.
Could a cable cause this or am I looking at a Speedometer repair?
Thanks for any input
When I'm shifting 1st, 2nd, 3rd and there is torque the speedometer reads zero. Let off the gas to shift and it jumps up to 40 MPH or so. In other words when I shift from say 2nd to 3rd it goes from zero to 40 and back to zero. After I'm in 4th gear it reads 40 - 50 MPH MAX.
Could a cable cause this or am I looking at a Speedometer repair?
Thanks for any input
Pro
Joined: Jul 2000
Posts: 654
Likes: 0
From: Now Frozen in Michigan
Re: Lets talk Speedometer (Mr D.)
I would first pull the speedo cable (insert) and inspect for any damage. If it's smooth and passes, clean with solvent, dry it, lube it and reinstall. I like to use synthetic grease, and just barely enough to coat it between your fingers. If your prob continues, my next step would be to inspect the driven speedo gear. And of course the last culprit is the speedo head itself.
Good Luck :chevy
Good Luck :chevy
Thread Starter
Team Owner
Joined: Mar 2002
Posts: 44,626
Likes: 1,826
From: Huntsville AL
Re: Lets talk Speedometer (ROD NOCK)
I pulled out the insert from the tranny and it did feel somewhat tight to turn. I cleaned it inside and out and lubed it. While I was there, I hooked up my drill to the speedo cable and it ran smooth from 0-80 MPH. After hooking everything up and a spin around the block it seems to be working better. The zero to 40 back to zero during shifting is much better and I'm seeing 60 MPH vice 40 that I was seeing. So, better but not fixed yet. I feel the Speedo Head is fine, it also has a new speedo cable. Any more thoughts?
Melting Slicks
Joined: Aug 2000
Posts: 2,310
Likes: 1
Re: Lets talk Speedometer (79corvette)
:iagree: Check the driven gear for incorrect installation or defects (missing teeth maybe).
After that, all you really have left is the drive gear attached to the trans output shaft. I replaced that gear on my '77. It wasn't too bad a job, but mine was the plastic gear held in with a clip versus the metal gear that's pressed on.
Good Luck. Keep us posted.
After that, all you really have left is the drive gear attached to the trans output shaft. I replaced that gear on my '77. It wasn't too bad a job, but mine was the plastic gear held in with a clip versus the metal gear that's pressed on.
Good Luck. Keep us posted.
