Speedometer needle jumpy
 

Hi, I was looking at a fully restored '66 FHC, done by a reputable restorer. I drove it and noticed that the speedometer needle was jumpy. It wouldn't stay still when speed was constant. I asked about this, and was told: "This is the best condition that is achievable. The original speedometer had a slight movement variation and this is most prominent on the early speedometers."

Does anyone know if the response is accurate? How difficult is it to replace the speedometer cable, to see if that is the problem?

Any ideas for a fix?

Thank you for your help.

John

John, the speedometer may jitter slightly but if you find it objectionable, it is probably too much. The cable can be unscrewed from the rear of the gauge easily. Tie some string to it then pull it through the fire wall from under the hood. The cable passes through two holes that do not line up exactly; the string will help with reinstallation. Pull the inner cable out of the outer jacket. Give it a light coating of grease then reassemble everything. Note there are grommets in each hole that probably became dislodged. The string should have caught them. Also make sure the cable is routed to avoid sharp bends. If that does not do it, a new cable is cheap. Other culprits include a right angled coupler where the cable connects to the transmission. It is accessed through a hole in the right side of the transmission tunnel. It is not cheap. Good luck.

Bill, thank you very much for your reply. Would it be possible to explain a little bit your "not cheap" second solution? I imagine that the "easy" fix was already considered.
Thank you again for your response.
John

Have not checked recently but as I remember it, maybe $200. Greasing the cable (lightly) has a good chance of doing it, I had the same issue when the cable was dry in places.

Thank you, Bill.

John,

I've owned and driven Jaguars for almost fifty years and do miss the way the speedometer needle used to sway gently in the 1960's and 70's models!

Some sway is not unusual at constant speed but jerky movement indicates a cable or angle drive fault as suggested.

Graham

Graham, thank you for this information. If the speedometer portion of the car is being rebuilt today, and properly working parts are used, and properly installed, shouldn't that eliminate the sway? Everything involved is mechanical (maybe the magnet isn't considered mechanical), but certainly no electronic gremlins would be involved. So if rebuilt properly today, should the sway be eliminated?

Thanks,
John

John,

I'd be surprised if it could be eliminated entirely. The best I've achieved is to go from "extremely annoying" to barely perceptible".

Graham

At least on a 1968 a perfectly steady speedo needle can be achieved. Mine was very erratic with a large "swing" of the needle at any constant speed. I had an instrument repair shop check the speedometer and make up a new cable. After reinstalling, the speedo stopped working. Back at the shop I was lucky enough to meet the ex-owner of the shop who diagnosed that the inner cable they supplied was too long and had put too much strain on the inner components of the speedo. He rebuilt the speedometer and made up a new inner cable. Since then, a very accurate and steady speedometer.