Speedometer half off
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Joined: Jan 2010
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Speedometer half off
My speedometer in a 76 Crewcab showes about 40 to 50 at 70 mph. It is not consistant at all it varies by about 10 mph when GPS says 70. Also the needle bounces about 2mph all the time. Does anyone have an idea on what is wrong
Senior User
Joined: Mar 2006
Posts: 212
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From: Morganton, NC
It is off that much most likely because the truck has been re-geared. The needle bounces most likely because the speedo gear in the transmission is wore.
Getting a new speedo gear with the right amount of teeth should fix your problem, but which one, I do not know.
Getting a new speedo gear with the right amount of teeth should fix your problem, but which one, I do not know.
Cargo Master
Joined: Apr 2009
Posts: 3,038
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From: South west Idaho
What is the rear gear ratio and how tall are your tires ? The needle doesent sound like it is to bad, but a worn out speedometer head will make the needle bounce around as well as not give the correct M.P.H. I would do as suggested and check the gear in the transmission first . A bad cable will make the needle bounce too . 
Jim
Jim
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The rear end is 3.73s and the tires are 265/75/16s. The truck was regeared from 4.10s but it didn't change the speedo that much years ago (15) when the it was geared different. And what throws me is that the speedo isn't consistant. It will be around 40 one day and then 50 the next when GPS says 70.
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