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Discussion Starter #1
Ok...First of all I am getting a 90 SC rear end and I will be putting 3.73 gears in it. Secondly I am putting the 145 speedo and taking my 120 out. Also I will be putting on some 245 40 or 45 on some 18s. What should I do about recalibrating my speedo. Should I even bother with taking the speedo out of a SC from behide the speedometer or from the end of the trans? Or can they recalibrate it when I get my ford chip in and not mess with the speedo from the SC? which will be the same time as I put my rear end in. Thanks.

-Brian
 

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Refrigerator Raider Hater
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145mph speedo: recalibration not nessessary
slightly (+/-3%) different tire height: recalibration not nessessary
different rear gears: recalibration via a speedo gear. You want a purple 21 tooth. see tech articles.

I believe fordchip can correct for a tire size other than stock height.
 

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Discussion Starter #3
I swore you would need the speedo behide the speedometer just to recalibrate the 145 tack.

But about that 21 purple tooth, isn't that for an SC auto or doesn't it matter? And who sells them? I searched online, but I can't find anything I need.

-Brian
 

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TbirdJLcustom said:
I swore you would need the speedo behide the speedometer just to recalibrate the 145 tack.

But about that 21 purple tooth, isn't that for an SC auto or doesn't it matter? And who sells them? I searched online, but I can't find anything I need.

-Brian
DOOZ17271B: 21 Tooth Speedometer Gear-3.73 Gears-Automatic(Purple) $14.99
need 4 speed

I think the Ford part number for the speedo gear is C8SZ-17271-B, however, please do not quote me. (PN taken from this thread)

You should be able to get the 21 tooth gear from any Ford dealership in your area. If not, try Fordparts.com or from 5 Star Ford.
 
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