Which cog to use for speedo after fitting 3.45 diff?

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DEVEL

Post subject: Which cog to use for speedo after fitting 3.45 diff?

Posted: Wed Jun 14, 2006 7:50 am

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Hi guys as the title suggests, which cog do i use to correct my speedo reading?
I now have a 3.45 LSD fitted with 17" rims. Im pretty sure i have to use the black 23 tooth one but am unsure..... i rang ford and asked them but they werent convincing as they said the 22 tooth is for 15's and the 23 tooth is for 16's. So which will be best for 17's???

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Disco Frank

Posted: Wed Jun 14, 2006 8:59 am

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black cog dude!

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DEVEL

Posted: Wed Jun 14, 2006 9:27 am

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thanks for the info!

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kezz

Posted: Wed Jun 14, 2006 12:03 pm

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im 99% sure its the grey tooth for 3.45 and 17inch wheels. thats what ford gave me.

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DEVEL

Posted: Wed Jun 14, 2006 12:13 pm

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so the grey one is the 22 tooth cog???

how accurate is your speedo now with the grey one?

anyone else know which is best?

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Steady ED

Posted: Wed Jun 14, 2006 12:17 pm

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I think you are supposed to use the grey one, apparently 225/50R16s are a slightly larger diameter then 205/65R15s and 234/45R17s, which are almost identical.
Having said that, I've got a black one with my 17's and 3.45 diff, and speedo is fairly accurate, AFAIK.
Have a play with the 'Speedo Calculator' in the Technical Documents section.

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eed-250

Posted: Wed Jun 14, 2006 2:23 pm

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ive got a black one too

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DEVEL

Posted: Wed Jun 14, 2006 2:39 pm

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i didnt know about the calculator - thanks!!!

however one thing is does anyone know what cog was used for my standard 3.08 diff?
and are 15s standard for a 96 EL Futura as i thought 16s were!!

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kezz

Posted: Wed Jun 14, 2006 4:17 pm

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i pulled a black cog outta my gearbox when the 3.08 was in there. i had 17's on my car too

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DEVEL

Posted: Mon Jun 19, 2006 9:58 am

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well new gear is in.... i went with the black one, speedo is about half a k out in my favour eg 100.5 on speedo actual speed is 100

thanks for everyones help.

just for future reference i pulled a brown 20 tooth gear out - it was matched with 3.08 originally

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