If you have never understood what is meant by “4.11
axle” or “4 to one” gears for a transfer case, or a “6.32 1^{st}
gear in a transmission, I will attempt to shed some light on this: “
4.11 ratio” means 4.11 turns of the pinion gear give one turn of the
ring gear. “4 to one” transfer case gears mean the for every 4 turns
of the transmission output shaft, the driveshaft will turn one time. In
“4 to one” the word “to” means exactly the same thing as the colon
(“:”) in “4:1”.
Numerically higher gear ratio, meaning it will
require more revolutions of the driveshaft to make one revolution of the
tire. A 4.10 axle, for example will require 4.10 turns of the driveshaft
to achieve 1 full rotation of the tires).
The “crawl ratio” tells the number of times the
engine turns over compared to the axles. A
crawl ratio of 20 means for every 20 revolutions of the engine, you
get one revolution of the tires. A crawl
ratio of 100 means for every 100 revolutions of the engine, you get one
revolution of the tires. The
crawl ratio is calculated in the lowest gear combination the vehicle has.
The math consists of multiplying all
of the gear ratios in the chain together. Example: Tranny has a 6.32 1^{st}
gear. Tcase has a 2.72 low range. The axle ratio is 4.56:1. The math is
thus: 6.32 x 2.72 x 4.56 =
78.39 crawl ratio. If you add a 4 to one auxiliary gearbox (such as a dual
Tcase or extreme underdrive) to this drivetrain, the math becomes: : 6.32 x 2.72 x 4 x 4.56 = 313.55 to one crawl ratio.
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