Gear Raito?

[Bad67MF]

I have a Currie 9" that is 10 yrs. old but never used. Currie could not tell me the raito from the #'s. Does anyone know how to figure the raito with out pulling the drop out & counting the ring & pinion or buying one of those paper gauges for $60.00 ??

[mustangII460]

Mark a axle and turn the pinion. See how many turns the pinion takes to complete one revolution of the axle. It will get you close.


Number of Turns Approximate Gear Ratio
2 - 3/4 2.72:1 or 2.77:1
3 - 0 3.07:1
3 - 1/2 3.54:1
3 - 3/4 3.73:1
4 - 0 4.10:1
4 - 1/2 4.56:1
4 - 3/4 4.88:1

[Rev]

Originally posted by mustangII460
Mark a axle and turn the pinion. See how many turns the pinion takes to complete one revolution of the axle. It will get you close.


Number of Turns Approximate Gear Ratio
2 - 3/4 2.72:1 or 2.77:1
3 - 0 3.07:1
3 - 1/2 3.54:1
3 - 3/4 3.73:1
4 - 0 4.10:1
4 - 1/2 4.56:1
4 - 3/4 4.88:1

That's right as long as both rear wheels are turning as in a limited slip or spool with both wheels off the ground. If only one wheel is off the ground and rotating, as in an open rear axle, then the wheel will make twice as many revolutions for the same number of pinion turns. You then need to count the number of pinion turns for 2 wheel revolutions and just use Franks chart. I agree that Currie 9" center sections are almost always going to be limited slip of some persuasion so what Frank says is certainly correct. I did have to do the two revolution thing when checking an open axle once though.

Rev

[Bad67MF]

: Thank you all. I got 3-3/4 turns=3.73:1 Next question, I am running an AOD w/ the low gear set (2.84) in my 67 Fastback even with these gears it seems a little lazy off the line.What rear gears would you recomend? Oh Ya 347,Edelbrock Alum.RPM heads w/2.02's & RPM int. w/650 Mighty Demon, Comp cam XE274H, 9.5:1 comp.,3000 stall,26" tall tires. I know the power band is around 2000-6000 rpm.

[Gearhead999]

Put a converter in it. It will get the car moving out of the hole.

[Bad67MF]

I've got a 3000 stall in it know,don't want to go higher on the street.

[KiltedBanshees93GT]

Originally Posted by Bad67MF

: Thank you all. I got 3-3/4 turns=3.73:1 Next question, I am running an AOD w/ the low gear set (2.84) in my 67 Fastback even with these gears it seems a little lazy off the line.What rear gears would you recomend? Oh Ya 347,Edelbrock Alum.RPM heads w/2.02's & RPM int. w/650 Mighty Demon, Comp cam XE274H, 9.5:1 comp.,3000 stall,26" tall tires. I know the power band is around 2000-6000 rpm.

What size rear?
With an AOD, at least 3.55, most folks go for 3.73, some go as far as 4.+. (ratios based on an 8.8 rear, approximations can be made to the gears available to your rear end)

J

[Bad67MF]

2.84 1st. gear AOD,3.73:1 rear.