Speedometer jumping and needle off
Thread Starter
Cruising
Joined: Jan 2008
Posts: 10
Likes: 4
Speedometer jumping and needle off
Hey guys,
I brought my 71 out for a walk today and when I got up to 40 the speedometer needle bounced way up to 120 and as I increased my speed it just jumped up to 160 and vibrated heavily with a squeaking noise. I was about 10 minutes away from home and before I got back, the needle popped off the speedometer!
First, what is the most likely culprit and what can I do to fix it and second, how do I get the needle back on!
Thanks,
Steelie
I brought my 71 out for a walk today and when I got up to 40 the speedometer needle bounced way up to 120 and as I increased my speed it just jumped up to 160 and vibrated heavily with a squeaking noise. I was about 10 minutes away from home and before I got back, the needle popped off the speedometer!
First, what is the most likely culprit and what can I do to fix it and second, how do I get the needle back on!
Thanks,
Steelie
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
If the needle came of that’s not a good sign.
We have a section on our web site that covers your odometer not working, but I have not had time to do one on other problems yet. This section will go in to enough detail that it might help you understand what happened.
In short, usually when the needle comes off the speed cup shaft has broken. It is possible for the needle to come off from the sudden jar to higher and lower speeds, but unlikely.
Did you hear a tinning noise while the needle was jumping? Is your odometer working?
The speedo needle is attached to the speed cup that is driven by magnetic force. This force is controlled by what is termed the first worm and magnet. The first worm and magnet is driven by the speedo cable and housed in an oil impregnated bushing. Over time this bushing wears out and usually the first indication is the odometer stops working.
If the bushing becomes so worn that the magnet starts hitting the speed cup (the tinning sound) it creates direct drive on the cup and slams it to the needle stop bar. If this happens the shaft breaks and the needle falls.
You can go to this link and we have a PDF file you can read and upload if you like. It will show you all the parts I’m talking about.
http://willcoxcorvette.com/repairand...lp.php?hID=145
Unfortunately, the speedo will have to come out of the car to be repaired.
You could have a cable issue and quite maybe the cable bound up and the release forcing the sudden speed increase and decrease, I suppose this could cause a loose needle to come off, but I’ve never seen this happen before.
Sincerely,
Willcox Inc
We have a section on our web site that covers your odometer not working, but I have not had time to do one on other problems yet. This section will go in to enough detail that it might help you understand what happened.
In short, usually when the needle comes off the speed cup shaft has broken. It is possible for the needle to come off from the sudden jar to higher and lower speeds, but unlikely.
Did you hear a tinning noise while the needle was jumping? Is your odometer working?
The speedo needle is attached to the speed cup that is driven by magnetic force. This force is controlled by what is termed the first worm and magnet. The first worm and magnet is driven by the speedo cable and housed in an oil impregnated bushing. Over time this bushing wears out and usually the first indication is the odometer stops working.
If the bushing becomes so worn that the magnet starts hitting the speed cup (the tinning sound) it creates direct drive on the cup and slams it to the needle stop bar. If this happens the shaft breaks and the needle falls.
You can go to this link and we have a PDF file you can read and upload if you like. It will show you all the parts I’m talking about.
http://willcoxcorvette.com/repairand...lp.php?hID=145
Unfortunately, the speedo will have to come out of the car to be repaired.
You could have a cable issue and quite maybe the cable bound up and the release forcing the sudden speed increase and decrease, I suppose this could cause a loose needle to come off, but I’ve never seen this happen before.
Sincerely,
Willcox Inc
