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Old 05-30-2005, 04:50 AM   #1
willow72
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rear gears?

im begining too think i dont know what gears i have. from listening to what everybody saying i should be turning around 2300 rpms at 70mph with a turbo 350 307 rear gears and 31 inch tires. but im not. im turning about 3000 rpms is there a easy way too find out what rear gears i have without pulling the cover off the rearend ? i guess the only thing im sure about my rearend is that its a 12 bolt thanks for any help, john
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Old 05-30-2005, 04:57 AM   #2
Pickemuptruck71
Coast 2 Coast in 61 mins.
 
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John, try this link lot of good info here for you http://67-72chevytrucks.com/vboard/s....php3?t=105927
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69 C20
71 C10 40 over 454, AT, 3.08 gears
71 Demon 340, 4spd, 4.56 gears
70 RoadRunner 440 6pack, 4spd, 4.10 gears
99 Dakota R/T 360, AT, 3.91 gears
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Old 05-30-2005, 09:58 AM   #3
Longhorn Man
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Why not drain the old oil that is only workin at 50% at best?
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Old 05-30-2005, 03:28 PM   #4
willow72
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im not understanding what they are saying in that link divide by what?
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Old 05-30-2005, 03:38 PM   #5
pjmoreland
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Here's an equation that will calculate your gear ratio.

Gear Ratio = (3000revs/min) x (1/70 mi/hr) x (60min/1hr) x (1mi/5280ft) x (1ft/12in) x (31in x 3.14)

Gear Ratio = 3.95

The problem with doing this calculation is that it doesn't take into account the slippage of the torque converter. My guess is that you have 3.73 gears.
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