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post #1 of 17 (permalink) Old 11-01-2006, 05:28 PM Thread Starter
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Differential Gearing Question

I am upgrading from 28 spline to 31 spline axles and so am considering a gear change since I am changing the pumpkin (9 inch) to a 31 spline.

I currently run 3.70 gears with 26.5" diameter M/T Streets. Since I drive it on the street a lot, I am considering changing to 3.25 gears which would lower my cruise rpm and possible improve gas milage. However, I am not sure how much it would impact 1/4 mile times. The car is about 3550 lbs. horsepower peak is 6200 rpm. If it amount to a couple of tenths its ok, but if more I will probably stay with the 3.70 gears. Please advise your thoughts.

Thanks,
James

Rest of combo is:

466 with ported DOVE's, exhausts opened to CJ, and 2.19" and 1.76" Manley valves.
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Matching valve springs with titanium retainers
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post #2 of 17 (permalink) Old 11-01-2006, 05:39 PM
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I can't tell you that but I can give you a formula that helps tell what gear ratio is optimum:

Elapsed Time X MPH = 1335 if the number is more than 1335 add more rear gear. If it is less than 1335, reduce rear gear. This helps find optimum gearing for the 1/4.



MPH= (Tire DiameterxRPM)/(Gear Ratiox336) this finds your mph at a certain rpm/gear ratio.

Might help you in making an educated decision.
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post #3 of 17 (permalink) Old 11-01-2006, 05:46 PM
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Going to the 3.25's probably won't change your trap speed by much, but your short times are gonna suck by comparison.

I used to concern myself with fuel economy..........then I realized that "BBF gas miser" was an oxymoron......kinda like "sanitary landfill" or "reality TV". :lol:

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post #4 of 17 (permalink) Old 11-01-2006, 05:52 PM Thread Starter
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Or

Or Military Intellegence? I hear ya.

Using jpierce55's formula, the optimums would be around 4.00. Maybe I should just go the other way and put in 4.11s and trailer it to the track.

James
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post #5 of 17 (permalink) Old 11-01-2006, 05:55 PM
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How about "bagpipe music"? :roll:

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post #6 of 17 (permalink) Old 11-01-2006, 05:58 PM
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Or maybe "Super Chevy"? Somebody stop me! :lol:

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post #7 of 17 (permalink) Old 11-01-2006, 05:59 PM Thread Starter
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Sorta

Sorta sounds similar to running over a cat slowly
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post #8 of 17 (permalink) Old 11-01-2006, 06:02 PM Thread Starter
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Here we go again

This is a typical 460ford.com string. We have gone from rear gears to bagpipes to squashed cats
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post #9 of 17 (permalink) Old 11-01-2006, 06:12 PM
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Where else can you find quality entertainment like this?..........and it's so afFORDable, too!

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post #10 of 17 (permalink) Old 11-01-2006, 06:36 PM Thread Starter
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Good one

Yes, it's aFORDable, but just think of all the professional comedians that we are putting out of work. Why they may be "driven" to enroll in the Betty "Ford" clinic.

Yuk yuk. We better stop or Chillie will disown us.
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post #11 of 17 (permalink) Old 11-01-2006, 06:52 PM
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Hey.......Fairlane62.....Do you currently drive one of those? I ask because I have a soft spot for a '62 Fairlane. When I was 17, I used a '62 Fairlane to keep myself in a PECK of trouble. :roll:

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post #12 of 17 (permalink) Old 11-01-2006, 07:09 PM
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Stand up comedy

you guys are great.
Why stop now?

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post #13 of 17 (permalink) Old 11-01-2006, 07:12 PM
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Because, just like Rodney Dangerfield........we don't get no respect.

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post #14 of 17 (permalink) Old 11-01-2006, 09:27 PM Thread Starter
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Yep

Either we're like Rodney Daingerfield and we get no respect. Or we're like the Rolling Stones and we get no satisfaction. Either way it's pretty bad since I highjacked my own thread.

Maverick,

Yes I do have a 62 Fairlane. It's a two door post. Basically a early version of a Thunderbolt clone except with a 466.

James
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post #15 of 17 (permalink) Old 11-02-2006, 05:10 PM
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Mine was a 2-dr post, too. I blew up three 260's (windows in the thinwall cylinders) before I built a 289. This was 1968. My girlfriend's dad ran a machine shop, and he fixed me up with the first set of 289 heads I ever saw with a port job snd 2.02 Chevy valves. Woof, that booger would go....just ask the Michigan State Police. :shock:

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