Gear Ratios Options

[BonzaiCelica]

I was wondering what the purpose of the final drive gear ratio?

also what is this? http://auctions.nengun.com/item/k113042803

[BonzaiCelica]

I got the information from this link : http://www.rubydist.com/Family/Power.html

A second way to improve acceleration is to put a higher (numerically) ratio final drive in the vehicle. The torque available at the drive wheels is the engine torque multiplied by the transmission ratio multiplied by the final drive ratio.
Let's just use some hypothetical numbers to make the math easy. Let's say for an example that the engine has 200 lb-ft of torque all across the usable speed range (a gross oversimplification); let's have a final drive ratio of 3:1, a rolling radius of 1.25' (15" radius, 30" diameter tire); and let's say that the transmission ratios are 3:1 (1st), 2:1 (2nd), 1.5:1 (3rd), 1:1 (4th), and .75:1 (5th).
-So, the torque available at drive wheels in first gear is 200 (engine torque) x 3 (first gear ratio) x 3 (final drive ratio) = 1800 lb-ft. (The force at the point where the drive wheels contact the road is a total of 1800 lb-ft / 1.25 ft (rolling radius) = 1440 lb.) If we change the final drive ratio to 4:1, the first gear torque will be 200 x 3 (first gear ratio) x 4 (final drive ratio) = 2400 lb-ft.
This is a 33% increase in drive wheel torque, and it will result in dramatically improved acceleration. (It will also increase engine speed on the highway, resulting in lower fuel mileage, increased noise & engine wear, and a lowered top speed of the vehicle.) The final drive ratio has no effect on the horsepower of the vehicle, but it does affect the torque available to the drive wheels.

Stock S54 Gear Ratios:

1st : 3.285
2nd: 1.960
3rd: 1.322
4th: 1.028
5th: .820
Final Drive: 4.176

Using this equation, (engine torque) x (first gear ratio) x (final drive ratio) = # of pounds. Then # of pounds / rolling tire radius in feet = gives you # of wheel torque.

I am using my current 215/45R17 tire size = 2.06 ft in diameter.

Final Drive 4.176 (Stock S54) = 1012.21 pounds

Final Drive 4.562 (96-2000 Rav4 E250) = 1105.78 pounds

Final Drive 4.933 (96-2000 Rav4 E250F) = 1195.70 pounds

Increase in torque from 4.176 - 4.529 is 9.24%.
Increase in torque from 4.562 - 4.933 is 8.92%
Increase in torque from 4.176 - 4.933 is 18.14%

Which means a 4.933 final drive in your s54 transmission will gain 27 ft lb torque + 152 = 179 ft lb tq


This post has been edited by BonzaiCelica: Oct 16, 2017 - 5:32 AM