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Author Topic:   Another speedo cable Question...
70 Pony
Gearhead

Posts: 1783
From: Glenmoore, PA, USA
Registered: Jan 2000

posted 02-26-2002 11:14 AM     Click Here to See the Profile for 70 Pony   Click Here to Email 70 Pony     Edit/Delete Message   Reply w/Quote
I think this may have been covered before, but you all know I'M SLOW !!!!
Is there a particular cable and gear replacement cable for a 70 Mustang that will convert an original 3.00 gear and 14" wheel to 3.55 gears and 15" wheels....or at least something close...without figuring out original tire diameters etc.....
Thanks...

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EDDIE D
Resto Mod '70 Sport Roof
Arrest Me Red
'02 GT, Torch Red

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SteveLaRiviere
Administrator

Posts: 29373
From: Saco, Maine
Registered: May 99

posted 02-26-2002 11:52 AM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
If you want it accurate, you do need to do the math, sorry.

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC

MCA Member # 47773

I once asked a man: "Who art thou, that ye may pass judgment upon others?" Then he added $75 to my fine...

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70 Pony
Gearhead

Posts: 1783
From: Glenmoore, PA, USA
Registered: Jan 2000

posted 02-26-2002 06:30 PM     Click Here to See the Profile for 70 Pony   Click Here to Email 70 Pony     Edit/Delete Message   Reply w/Quote
OK STEVE....THE MATH ?????
Get the original wheel/tire dimensions for the oem 14"ers, compare them to the new wheel/tire dimensions with the 15's...anything else...some algebraic formula for comparing the 3.00's to the 3.55's ????
Or is it just tire dimensions plus compensating for the 3.55's ??
Thank You Teacher.....

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EDDIE D
Resto Mod '70 Sport Roof
Arrest Me Red
'02 GT, Torch Red

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SteveLaRiviere
Administrator

Posts: 29373
From: Saco, Maine
Registered: May 99

posted 02-26-2002 06:51 PM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
If you can supply the tire sizes, we can take it from there.

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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC

MCA Member # 47773

I once asked a man: "Who art thou, that ye may pass judgment upon others?" Then he added $75 to my fine...

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70 Pony
Gearhead

Posts: 1783
From: Glenmoore, PA, USA
Registered: Jan 2000

posted 02-27-2002 01:51 PM     Click Here to See the Profile for 70 Pony   Click Here to Email 70 Pony     Edit/Delete Message   Reply w/Quote
You need old versus new or just new....
I know I'm at 26" diameter now Steve...thanks.

------------------
EDDIE D
Resto Mod '70 Sport Roof
Arrest Me Red
'02 GT, Torch Red

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SteveLaRiviere
Administrator

Posts: 29373
From: Saco, Maine
Registered: May 99

posted 03-01-2002 01:45 PM     Click Here to See the Profile for SteveLaRiviere   Click Here to Email SteveLaRiviere     Edit/Delete Message   Reply w/Quote
Well, I looked up a 205/75-14 which is close to the E78-14s they used to use and those are 26.11 " so your tire diameter hasn't changed much.

You can even pretty much use the formula on my speedometer gear page:
https://mustangsandmore.com/ubb/speedogear.html

code:

We'll assume you had a 3.00 gear ratio, and you've changed them to a 3.50 ratio.

Here's the formula;

So, if you had a 3.00 and you now have a 3.50, and you have an 18 tooth driven
gear;

3.00 3.50
----- = ------
18 X


if you cross multiply (18 x 3.50)/3 = 21

So you need a 21 tooth gear.


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'70 Mustang Mach 1 M code 351C 4V/FMX/3.25 open
'72 Mustang Sprint Coupe 351C 4V/FMX/4.30 Trac Lok
'94 F-150 XL 5.8L/E4OD/3.55 Limited Slip
'97 Probe GTS 2.5L DOHC

MCA Member # 47773

If the human brain were so simple that we could understand it, we would be so simple that we couldn't.

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70 Pony
Gearhead

Posts: 1783
From: Glenmoore, PA, USA
Registered: Jan 2000

posted 03-02-2002 05:19 PM     Click Here to See the Profile for 70 Pony   Click Here to Email 70 Pony     Edit/Delete Message   Reply w/Quote
Thanks Steve...that'll be close enough for "Government Work" !!!!!!

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EDDIE D
Resto Mod '70 Sport Roof
Arrest Me Red
'02 GT, Torch Red

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