Plug in required values to compare RPM under variable axle, transmission, and tire setups.
* Note - Advertised tire sizes are nominal values. For accurate results, measure actual tire height to the nearest 1/4 of an inch.
Common Transmission Ratio Chart
Transmission Model |
1st |
2nd |
3rd |
4th |
5th |
6th |
R |
SM465 |
6.55 : 1 |
3.58 : 1 |
1.57 : 1 |
1.00 : 1 |
--- |
--- |
6.09 : 1 |
SM420 |
7.05 : 1 |
3.57 : 1 |
1.70 : 1 |
1.00 : 1 |
--- |
--- |
6.78 : 1 |
NP435* |
6.68 : 1 |
3.34 : 1 |
1.66 : 1 |
1.00 : 1 |
--- |
--- |
8.26 : 1 |
T-18 |
6.32 : 1 |
3.09 : 1 |
1.69 : 1 |
1.00 : 1 |
--- |
--- |
7.44 : 1 |
NV4500* |
5.61 : 1 |
3.04 : 1 |
1.67 : 1 |
1.00 : 1 |
0.75 : 1 |
--- |
5.61 : 1 |
NV5600 |
5.63 : 1 |
3.38 : 1 |
2.04 : 1 |
1.39 : 1 |
1.00 : 1 |
0.73 : 1 |
5.63 : 1 |
ZF S5-42/S5-47 |
5.72 : 1 |
2.94 : 1 |
1.61 : 1 |
1.00 : 1 |
0.76 : 1 |
--- |
5.24 : 1 |
ZF S6-650 |
5.79 : 1 |
3.30 : 1 |
2.10 : 1 |
1.31 : 1 |
1.00 : 1 |
0.72 : 1 |
5.23 : 1 |
GM TH350 |
2.52 : 1 |
1.52 : 1 |
1.00 : 1 |
--- |
--- |
--- |
1.93 : 1 |
GM TH400 |
2.48 : 1 |
1.48 : 1 |
1.00 : 1 |
--- |
--- |
--- |
2.07 : 1 |
GM TH700R4 |
3.059 : 1 |
1.625 : 1 |
1.00 : 1 |
0.696 : 1 |
--- |
--- |
2.294 : 1 |
GM 4L80E/4L85E |
2.48 : 1 |
1.48 : 1 |
1.00 : 1 |
0.75 : 1 |
--- |
--- |
2.07 : 1 |
Chrysler TorqueFlite 727 |
2.45 : 1 |
1.45 : 1 |
1.00 : 1 |
--- |
--- |
--- |
2.22 : 1 |
Ford C4/C6 |
2.46 : 1 |
1.46 : 1 |
1.00 : 1 |
--- |
--- |
--- |
2.18 : 1 |
Ford AOD/AODE |
2.40 : 1 |
1.47 : 1 |
1.00 : 1 |
0.67 : 1 |
--- |
--- |
2.00 : 1 |
Ford E4OD |
2.71 : 1 |
1.54 : 1 |
1.00 : 1 |
0.71 : 1 |
--- |
--- |
2.16 : 1 |
Ford 4R70W |
2.84 : 1 |
1.55 : 1 |
1.00 : 1 |
0.70 : 1 |
--- |
--- |
2.23 : 1 |
Ford 4R100 |
2.71 : 1 |
1.54 : 1 |
1.00 : 1 |
0.71 : 1 |
--- |
--- |
2.88 : 1 |
Gear Ratio Terms & Jargon
Low: A low gear ratio is numerically high. For example, a 4.56:1 ratio is lower than a 3.73:1. Lower gearing results in a higher mechanical advantage and therefore higher drive torque output. At the same time, lower gearing increases engine speed for a given vehicle speed.
High: A high gear ratio is numerically low. For example, a 3.73:1 ratio is higher than a 4.56:1 ratio. Higher gearing results in a lower mechanical advantage and therefore lower drive torque output. At the same time, higher gearing reduces engine speed for a given vehicle speed.
Tall: "Tall" gearing refers to a relatively high drive ratio. The taller the ratio, the higher the theoretical top speed and the lower the cruising rpm for a given vehicle speed. Tall gearing favors fuel economy over performance.
Short: "Short" gearing refers to a relatively low drive ratio. The shorter the ratio, the lower the theoretical top speed and the higher the cruising rpm for a given vehicle speed. Short gearing favors acceleration and crawling performance, but at the expense of lower fuel economy.
Direct Drive: Refers to a gear ratio of 1:1. The input shaft and output shaft rotate at equal speeds.
Underdrive: A ratio is "underdriven" if the output shaft spins at a slower speed than the input shaft. At a 1:1 ratio, the input and output shafts of a gearset spin at equal speeds. At a 2:1 ratio, the output shaft speed is 50% less than the input shaft speed. Underdriven gearsets provide a greater degree of mechanical advantage.
Overdrive: A ratio is "overdriven" if the output shaft speed is greater than the input shaft speed. At a 1:1 ratio, the input and output shafts of a gearset spin at equal speeds. At a 0.75:1 ratio, the output shaft speed is 25% greater than the input shaft speed. Transmission overdrive gearsets are used to reduce rpm at cruising speeds.