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Author
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Topic: Gear Ratios for 66 4spd
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BornInAFord
Journeyman Posts: 5
From: Bend, OR, USA
Registered: Dec 2002
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posted 12-17-2002 03:07 PM
  
I just inherited a 66 A-code with a 4spd from my grandfather-in-law. He has had the car since new and has all the reciepts and paperwork on it. My question for any of you: How do you calculate gear ratios? It originally came with a 3.00 ratio rear-end, since changed to a much lower (3.89?). 2nd and 3rd spds are also replaced. Unfortunately, all the reciepts say is what was done, not what each was changed to. According to my driving, the current final gearing is (approx. mph/1000rpm) 6.7, 8.7, 11.0, 18.8. Is this normal or a little close in spacing? sorry for the long post.
Daniel
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BornInAFord
Journeyman Posts: 5
From: Bend, OR, USA
Registered: Dec 2002
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posted 12-17-2002 03:35 PM
I should be a little more specific. I believe that 4th is 1.00:1, so I could calculate the rear-end ratio based on the 18.8mph/1000rpm (if I had the formula). I then could use this rear-end ratio to calculate what the other transmission speeds are and decide whether to change 2nd and 3rd back to original (if different) and/or change the rear-end or change to a T-5. I just feel that the 1st 3 speeds are a little too close to be from the factory and that the final drive ratio is too low to be a very economical highway cruiser. I do like the performance, however, despite not having a passing gear (3rd being too low geared).
Daniel 
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steve'66
Gearhead Posts: 4912
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 12-17-2002 04:04 PM
Here you go,http://www.randysringandpinion.com/calculators.shtml SteveW
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BornInAFord
Journeyman Posts: 5
From: Bend, OR, USA
Registered: Dec 2002
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posted 12-17-2002 04:21 PM
4.11:1 rear-end! Looks like a candidate for a T-5 version. 
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rockafellz
Gearhead Posts: 631
From: San Lorenzo, CA, USA
Registered: Aug 2001
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posted 12-17-2002 04:26 PM
Welcome to M&M!! I'd keep the 4spd. I've heard it's stronger than the T-5. Just me... Erik ------------------
1966 Ford Mustang 2+2
Mine - Restomod in Progress 1966 Ford Mustang Coupe
Dad's - Original Unrestored
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BornInAFord
Journeyman Posts: 5
From: Bend, OR, USA
Registered: Dec 2002
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posted 12-17-2002 05:09 PM
quote:
Originally posted by rockafellz:
Welcome to M&M!! I'd keep the 4spd. I've heard it's stronger than the T-5. Just me... Erik
Thanks for the welcome. I felt I sat on the sidelines for too long. It WOULD be easier and cheaper to swap the rear-end. I'm still wondering about the tranny gear splits, though. It seems to waste a gear--I shift, then almost immediately shift again. I'm not used to 4spds (my 67 has a C4 with 2.79 gearing), but I thought that even the close ratio 4spds had wider gear splits than mine does. Daniel
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Moneymaker
Administrator Posts: 16289
From: Lyons, IL, USA
Registered: May 99
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posted 12-17-2002 05:26 PM
Welcome to M&M  The top loader is much stronger than a T-5.
If you have a 2.78 low gear wide ratio version then you have a bonus. ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
www.moneymakerracing.com
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