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Speedo Question

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Old Jun 16, 2021 | 03:30 PM
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78 with automatic transmission. At slow speed the needle barely moves. With car at 50 mph, the needle waivers around 30 mph but goes no higher. Not sure if it would be the the speedo cable or the gauge itself. Any help would be appreciated. Thanks.
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Old Jun 16, 2021 | 06:05 PM
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Originally Posted by GX Ame
78 with automatic transmission. At slow speed the needle barely moves. With car at 50 mph, the needle waivers around 30 mph but goes no higher. Not sure if it would be the the speedo cable or the gauge itself. Any help would be appreciated. Thanks.
If you're sure the cable is engaged at both ends, Cable problem would be no operation or an oscillating needle. Sounds like the speedo. They can be cleaned up and repaired.

Last edited by Mrvettenick; Jun 16, 2021 at 06:08 PM.
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Old Jun 16, 2021 | 08:44 PM
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Remove the cable at the transmission end. Spin the cable with a drill. Same issue, it's the speedometer. Otherwise check the driven gear in the transmission.
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Old Jun 16, 2021 | 08:49 PM
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Yes. Sometimes the square-drive recess in the trans gear can get cracked so that the cable will work OK at low speeds, but start to slip and spin inside that recess at higher speeds.
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Old Jun 17, 2021 | 04:50 PM
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Thanks for the replies. I'll check it out.
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Old Jun 17, 2021 | 05:17 PM
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Be careful with the driven gear - it's fairly easy to push it in too far and have it drop into the transmission tail assembly. Then after a few hours of trying to fish it out, just put another one in. It doesn't seem to bother the tranny any to have the other one floating around in there.
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