explain the numerical value of gears???
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98COBRA281
10 Year Member
4.10- the drive shaft spins 4.1 times to make the tire spin one revolution
3.73- the drive shaft spins about 3-3/4 times to make the tire spin one revoluton
3.73- the drive shaft spins about 3-3/4 times to make the tire spin one revoluton
Pearl02
Member
Yea, what he said. With all things being equal(cars and drivers other than gears) the car with the 4.10's will get to the quarter mile quicker. Pearl02.
trinity_gt
10 Year Member
As stated above, the value is a ratio describing the number of rotations the driveshaft would make for every rotation of the ring gear (and thus the road wheels.) Like any gear ratio, the number derives by dividing the number of teeth on the ring gear by the number of teeth on the pinion. A 4.10 gear will have 41 teeth on the ring and 10 on the pinion giving 41/10 or 4.10:1. A 3.73 will have 41 and 11 respectively, giving 41/11 or 3.73:1. There are basically two effects that fall out of this ratio:
First is the torque multiplication that occurs through the final drive gearset. A 3.27:1 gear ratio will multiply the torque from the driveshaft by 3.27 times. This means that if the driveshaft sees 300 ft-lbs the axles will see 981 ft-lbs. For a 4.10 gear set, the axles would see 1230 ft-lbs. Obviously, for heavy cars (for example), there's a benefit to going to a lower (higher numerically) gearset in terms of multiplying the engine torque to get the car moving. Think of how sprightly the car feels in 1st gear compared to 3rd...
Second is that the gear set divides the driveshaft RPM down by the same numerical value. A 3000RPM driveshaft speed with a 3.27 gearset equals an axle RPM of ~917RPM. With a 4.10 gear, you'd see only ~732RPM at the axle. This means that for any given engine RPM, the car will be moving slower in terms of speed. Again, consider the speed of the car when 1st gear is selected versus the speed of the car when 3rd gear is selected.
It's not always true that a 4.10 car will reach the quarter mile marker from a standstill faster than, say, a 3.55 car. The overall combination -- transmission gear ratios, tire height, engine RPM range and so on -- all play into selecting a final drive ratio to minimize the ET.
Most people that don't race have other factors to consider. For example, highway RPM: A 4.10 gearset will result in 25% more engine RPM than a 3.27 (4.10/3.27) so if your car cruises at 2000 with 3.27s, expect it to be at 2500 with 4.10s. For some the added RPM, noise and so on may be objectionable. Then again, 4.10s will make the car feel faster away from lights and in town which is why so many recommend them. The 4.6L engine is somewhat torque challenged so the additional torque multiplication offered by a steep gearset really helps the feel of the car around town.
First is the torque multiplication that occurs through the final drive gearset. A 3.27:1 gear ratio will multiply the torque from the driveshaft by 3.27 times. This means that if the driveshaft sees 300 ft-lbs the axles will see 981 ft-lbs. For a 4.10 gear set, the axles would see 1230 ft-lbs. Obviously, for heavy cars (for example), there's a benefit to going to a lower (higher numerically) gearset in terms of multiplying the engine torque to get the car moving. Think of how sprightly the car feels in 1st gear compared to 3rd...
Second is that the gear set divides the driveshaft RPM down by the same numerical value. A 3000RPM driveshaft speed with a 3.27 gearset equals an axle RPM of ~917RPM. With a 4.10 gear, you'd see only ~732RPM at the axle. This means that for any given engine RPM, the car will be moving slower in terms of speed. Again, consider the speed of the car when 1st gear is selected versus the speed of the car when 3rd gear is selected.
It's not always true that a 4.10 car will reach the quarter mile marker from a standstill faster than, say, a 3.55 car. The overall combination -- transmission gear ratios, tire height, engine RPM range and so on -- all play into selecting a final drive ratio to minimize the ET.
Most people that don't race have other factors to consider. For example, highway RPM: A 4.10 gearset will result in 25% more engine RPM than a 3.27 (4.10/3.27) so if your car cruises at 2000 with 3.27s, expect it to be at 2500 with 4.10s. For some the added RPM, noise and so on may be objectionable. Then again, 4.10s will make the car feel faster away from lights and in town which is why so many recommend them. The 4.6L engine is somewhat torque challenged so the additional torque multiplication offered by a steep gearset really helps the feel of the car around town.
Pearl02
Member
I agree with you 100%. However, I did use the phrase "all things being equal" the car with 4.10's will finish the quarter before the one with 3.73's will. If you start to throw in other variables, then the one with 4.10's will not always finish ahead of the one with 3.73's. Good post. Pearl02.
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