 Bouncing tach and speedo, where to start |
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| hndyhrr |
 Apr 16 2026, 07:38 PM
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#1
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Senior Member  Group: Members Posts: 673 Joined: 1-September 13 From: central point,oregon Member No.: 16,332 Region Association: Pacific Northwest 
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Last time i drove the pumpkin got almost home and had the fuel pump and master cylinder go side ways on me.
New MC is installed and brakes bled. new fuel pump and gas tank going in this weekend. During that drive I noticed that the tach and the speedo were bouncing alot. The speedo milage has never worked but the trip milage did. Could this be a ground issue? WCR is coming up and need to have it all taken care of. Thanks guys Renee |
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| barefoot |
Apr 17 2026, 06:42 AM
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Senior Member Group: Members Posts: 1,499 Joined: 19-March 13 From: Charleston SC Member No.: 15,673 Region Association: South East States
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Speedo is not electric, look for a twisted speedo cable back at the tranny.
My speedo angle drive on the tranny had got loose & rotated so the cable got kinked. had to get new speedo drive gear sequently. OR if you're just lucky just lube the cable from the speedo end. (IMG:style_emoticons/default/smile.gif) Barefoot |
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| porschetub |
Apr 17 2026, 04:26 PM
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914 Guru Group: Members Posts: 5,082 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
QUOTE(hndyhrr @ Apr 17 2026, 01:38 PM)  Last time i drove the pumpkin got almost home and had the fuel pump and master cylinder go side ways on me. New MC is installed and brakes bled. new fuel pump and gas tank going in this weekend. During that drive I noticed that the tach and the speedo were bouncing alot. The speedo milage has never worked but the trip milage did. Could this be a ground issue? WCR is coming up and need to have it all taken care of. Thanks guys Renee A bouncing tacho can be wiring issue from the engine bay (coil ) to gauge ,bad earth etc or the gauge itself is failing and has lost its stability which means there is a fault in the 50yr old driverboard . Speedo will be a bad cable or broken/misaligned drive cog/s ,cheers. |
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| jim_hoyland |
Apr 17 2026, 05:51 PM
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#4
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Get that VIN ? Group: Members Posts: 10,050 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California
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I remedied a bouncing speedo with a cable lubricant.
Disconnected the cable at the gauge and put the lubricant into the cable, As I remember it took a fair amount and was difficult holding the cable in a suitable position; now, the gauge is super smooth above 15 mph Attached image(s) 
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