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07-09-2009, 08:39 PM
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#1 |
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Senoir Member
Join Date: Mar 2002
Location: Rock Hill, SC USA
Posts: 1,214
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How to figure out the Speedo gears.
Can someone explain how to determine the proper speedo gears if changing rear axle gears. I have the 402/th400 2wd with 3.07 posi & 29" tires (275-60-15), and I believe the speedo is correct now. I'm thining of going to a 3.42 ratio, but all the other stuff with stay the same. This will cause the speedo to be off one way or the other.
I keep meaning to put the GPS in the truck and check the speedo, but you know.....
__________________
67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424 |
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07-09-2009, 08:44 PM
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#2 |
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Registered User
Join Date: Jan 2008
Location: Tejas
Posts: 691
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Re: How to figure out the Speedo gears.
I think bowtieoverdrives.com has shows exactly what kind you need
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'72 cheyenne super step, '05 long bed gmc |
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07-09-2009, 08:54 PM
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#3 |
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The Older Generation
   
Join Date: Aug 2006
Location: Montezuma, Iowa
Posts: 25,646
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Re: How to figure out the Speedo gears.
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Here are a couple of sites that have calculators... http://www.bgsoflex.com/speedo1.html http://www.transmissioncenter.net/sp...n_______va.htm LockDoc
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Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - |
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07-09-2009, 11:13 PM
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#4 |
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Senoir Member
Join Date: Mar 2002
Location: Rock Hill, SC USA
Posts: 1,214
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Re: How to figure out the Speedo gears.
Thanks, Will check them out.
__________________
67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424 |
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07-10-2009, 06:49 AM
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#5 |
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Senior Member
Join Date: Apr 2005
Location: Joppa, Maryland
Posts: 4,408
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Re: How to figure out the Speedo gears.
Here's a site I used. http://novaresource.org/speedo.htm
Also, here's a short write up I did. http://67-72chevytrucks.com/vboard/s...56#post3347056
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1997 GMC Sierra Ext 1965 Mustang |
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07-11-2009, 10:28 PM
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#6 |
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Senoir Member
Join Date: Mar 2002
Location: Rock Hill, SC USA
Posts: 1,214
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Re: How to figure out the Speedo gears.
Great info, Thanks.
__________________
67 Chevy, Small back glass, Factory 4WD, Factory Shortbed, Factory V8, Lifted 4" 70 GMC Sierra Grande, Factory Shortbed, Factory 402/400 turbo, Super Custom Interior. Numbers matching with SPID & Build Sheet. 68K Original Miles. Restored 2010 70 GMC Restoration Pictures http://67-72chevytrucks.com/gallery/...00&ppuser=4424 |
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