dumb question, gear ratio

Clutch, transmission, rear axle

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OldBluef100
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dumb question, gear ratio

Post by OldBluef100 »

Sorry for this dumb question guys, im currently running highways gears and i wanna know about what ratio they are so i can see how much i should change them. I have a 3 speed c6. At 5 grand in second im doing about 100-110, its impossible for me to top out my truck....and i wanna get good quarter mile/ street gears. If anyone could give me a shout on what they think my gears are that would be cool. Thx.
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BobbyFord
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Post by BobbyFord »

Need more info, like tire size. You may have 3.00:1 or taller in there now. Which are prolly not stock.
OldBluef100
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re: dumb question, gear ratio

Post by OldBluef100 »

Sorry i was in a hurry i forgot to mention they are not stock. Thier where 4:10 in thier and it was to low so the PO slapped in some highway gears, i just cant figure about what ratio. I have 31x11.5 and not to sure in front i believe 29x10.5

Thanks again!
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Joshpow
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re: dumb question, gear ratio

Post by Joshpow »

I'd use a 3.50 or 3.70 ratio if it were going to do much highway travel. That way the fuelmileage would be pretty good, but it also would be lower geared for better takeoff. The 3.70 would give better takeoff. The 3.50 would give better fuel mileage while cruising. I run 3.50's in my 72 302 c4.
Josh

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DuckRyder
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re: dumb question, gear ratio

Post by DuckRyder »

What is your RPM in 3rd (1:1) at 60 miles per hour?
Robert
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OldBluef100
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re: dumb question, gear ratio

Post by OldBluef100 »

id say 1300 to 1800 at 60mph in third. Thanks for all the input guys!
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Re: re: dumb question, gear ratio

Post by DuckRyder »

OldBluef100 wrote:id say 1300 to 1800 at 60mph in third. Thanks for all the input guys!
That doesn't help alot,

assuming a truly 31" tall tire.

1300 = 2.00:1 (not likely)
1800 = 2.77:1 (more likely)

http://www.4lo.com/calc/gearratio.htm

Really if you want to get close, you should look up your specific rear tire brand and see what they say the exact tire height is, then get your exact speed (GPS, stop watch on mile markers ect) and the more accurate your information the more exact the calculation will be.

There is also a table here that might help.

http://www.4lo.com/calc/geartable.htm
Robert
1972 F100 Ranger XLT (445/C6/9” 3.50 Truetrac)

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OldBluef100
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re: dumb question, gear ratio

Post by OldBluef100 »

Thanks for the info!
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