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Old 06-17-2012, 09:10 PM   #1
spdway1
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Default Speedometer Question

We changed the rear end ring and pinion, changed the speedometer gear to compensate for the different gear ratio. The speedometer now bounces back and fourth, I took the cable out, it is well lubricated, took the bottom side apart, everything seems ok. At about 33-36 it stops bouncing and reads accurate and at 50-55 it stops bouncing and reads accurate.
Now where do I need to look for a problem? Thank you.
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Old 06-17-2012, 09:24 PM   #2
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Default Re: Speedometer Question

If it is not fully in the head it will do this. I have made a spacer and placed at the end of the cable at the transmission to force the cable to the top. Usually use a 10/32 bolt about quarter of an inch in length.
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Old 06-17-2012, 09:42 PM   #3
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Default Re: Speedometer Question

What are you calling the head? Thank you.
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Old 06-18-2012, 12:40 AM   #4
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Default Re: Speedometer Question

Mine dd that. I loosened off the coupler where it screws into the speedometer housing. My theory is that the cable was too long. I have a mitchel overdrive so it is a different setup. However, it might be worth a try.
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Old 06-18-2012, 08:01 AM   #5
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Default Re: Speedometer Question

seems the cable is still binding "somewhere". Loosing it could be the ticket is the length is off a little. Also, check the cable along the length for any potential binds.
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Old 06-18-2012, 10:00 AM   #6
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Run it at a steady speed with a drill and see if it still bounces to see if it's cable related or head related.
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Old 06-18-2012, 01:35 PM   #7
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Default Re: Speedometer Question

Where the cable connects to the speedometer.
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Originally Posted by spdway1 View Post
What are you calling the head? Thank you.
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Old 06-18-2012, 01:41 PM   #8
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Default Re: Speedometer Question

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Originally Posted by Mitch//pa View Post
Run it at a steady speed with a drill and see if it still bounces to see if it's cable related or head related.
To get it turning the correct direction, you have to run your drill in reverse.
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Old 06-18-2012, 01:48 PM   #9
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Default Re: Speedometer Question

I had the bouncing problem after 25 mph. Took the cable off at the trans and used a cordless drill in reverse. All was fine till I put some upward pressure on the cable and it started bouncing. The cable was too long so I cut about 1/4 inch off and that solved it. No bouncing now.
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Old 06-28-2012, 08:45 AM   #10
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Default Re: Speedometer Question

I've had the bouncing speedometer issue for a long time but after reading this thread I too have been working on fixing it. Running it with a drill shows it reading steady. So I will next try the loosening cable trick before I cut the cable.

While I'm under there I'm working on that radius ball (from another thread).
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Old 06-28-2012, 09:10 PM   #11
spdway1
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Default Re: Speedometer Question

I loosend the end at the bottom, no improvement.
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Old 06-30-2012, 10:44 AM   #12
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Default Re: Speedometer Question

Same here. I loosened the cable at the torque tube which should relieve binding if it is too long, but that didn't help.
I also noticed that I had the cable clamp on the lower frame rail instead of the upper, so I moved it. Now I know why I put it on the lower, there was a bolt hole there that seemed right and the splash shield is kinda blocking the upper hole - but I got it in.
After all this the speedometer might be worse. It sits on zero alot and jumps up and down from 20-25..crazy thing.
I have the floor board out now and am going to get in there with the drill again.

Has anyone pulled the inner shaft out of the speedometer cable while its in the car? Is that a bad idea?
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Old 06-30-2012, 07:28 PM   #13
Tom Wesenberg
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Default Re: Speedometer Question

Pulling the inner cable out shoukd be no problem whether it's in the car or out.
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Old 07-01-2012, 12:33 AM   #14
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Default Re: Speedometer Question

The speedo on my coupe would only show about 20 mph even tho I was going about 50,then it would stay at 0 & once in a while jump up & down.Turned out the cable casing had a kink in it & the driven shaft in the"turtle" had the square hole worn out.I think the kink in the hsg put a strain on the cable & wore out the shaft for the cable end.
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Old 07-04-2012, 02:17 PM   #15
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Default Re: Speedometer Question

The Trip meter and odometer work fine, speedometer still bouncing. ERRRR...
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Old 07-04-2012, 03:24 PM   #16
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Default Re: Speedometer Question

Too sharp of a bend in the cable, if the cable was bent too sharp and straightened out the inner part can still have a kink ---pull the inside out, clean it off, roll it laid out straight on a table, if there are any bends or kinks straighten them out so the inner cable rolls smoothly across a table, check that the outer part installed has no curve to less than a 7" radius, re-lube the cable
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Old 07-05-2012, 10:08 AM   #17
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Default Re: Speedometer Question

spdway1, have you run your speedometer on a drill and its steady? Mine is, so I reluctantly pulled the instrument panel and then the speedometer. Took the thing apart and lightly oiled it. I noticed before removing it that if I let it rest on zero and start the drill slowly ramping up, it stays on zero until I tap the speedometer or if I gun the drill fast - it's like it sticks on zero. Once it's off of zero, it acts smooth.
I haven't driven the Model A yet to see if oiling the speedometer has done any good. However I did get a free app for the iphone that will measure mph, so I'm ready. Testing it in my regular car shows its within 1 mph.
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Old 07-05-2012, 08:08 PM   #18
spdway1
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Default Re: Speedometer Question

My helper will be here this weekend, I am going to try the drill in reverse from the bottom under the car.
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Old 07-12-2012, 10:32 PM   #19
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Default Re: Speedometer Question

OK, I was finally able to watch the speedometer cable turn while the car is moving. I have the floorboard out and the cable loose, and I got my sweetie to drive while I watched. I could see that the problem is the worm gear, which explains why the speedometer acts right when powered by a drill.

So now the question is to find out why the worm gear is stopping - missing teeth?
I could see that it has a lot of end play. Now to dig into it this weekend. Hopefully I can rebuild the little gearbox.

Spdway1 - how are you coming along?
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Old 07-12-2012, 11:17 PM   #20
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Default Re: Speedometer Question

By worm gear do you mean the driven gear in the "turtle"?If so, you could remove the gasket on the turtle and just use a bit of silicone and when you install it,it will fit closer to the drive gear on D S.Best repair is to repair the unit or replace with a better one.
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