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  Gear Ratios for 66 4spd

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Author Topic:   Gear Ratios for 66 4spd
BornInAFord
Journeyman

Posts: 5
From: Bend, OR, USA
Registered: Dec 2002

posted 12-17-2002 03:07 PM     Click Here to See the Profile for BornInAFord     Edit/Delete Message   Reply w/Quote
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

posted 12-17-2002 03:35 PM     Click Here to See the Profile for BornInAFord     Edit/Delete Message   Reply w/Quote
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

posted 12-17-2002 04:04 PM     Click Here to See the Profile for steve'66   Click Here to Email steve'66     Edit/Delete Message   Reply w/Quote
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

posted 12-17-2002 04:21 PM     Click Here to See the Profile for BornInAFord     Edit/Delete Message   Reply w/Quote
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

posted 12-17-2002 04:26 PM     Click Here to See the Profile for rockafellz   Click Here to Email rockafellz     Edit/Delete Message   Reply w/Quote
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

posted 12-17-2002 05:09 PM     Click Here to See the Profile for BornInAFord     Edit/Delete Message   Reply w/Quote
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

posted 12-17-2002 05:26 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
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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