9 Specifications

V*1100 Rear end: 32 teeth on ring gear and 11 on pinion = 2.90909 ~ 2.91

Gear Ratio Explanation:

The term gear ratio simply means the ratio of # of teeth between two meshing gears. In a system where two gears mesh together, one of the gears will have power applied to it (the drive gear) and the other gear (the driven gear) will be turned by the drive gear.

The ratio is simply the number of teeth on the driven gear divided by the number of teeth on the drive gear. In the case of rear axles, the pinion gear (the drive gear) has X number of teeth and the ring gear (the driven gear) has Y number of teeth. If we divide Y by X (Y/X) then we get the gear ratio.

For example, a ring gear that had 43 teeth and a pinion that had 11 teeth would be a gear ratio of 3.916 (~3.92). A ring gear that has 39 teeth and a pinion that has 11 teeth would have a gear ratio of 3.545 (~3.55). I dont know if this is the actual number of teeth in our trucks, but its a possibility.

If you have a drive gear that has MORE teeth than the driven gear than you have an overdrive system (the gear ratio is less than 1:1, or is often referred to as 0.72, etc.) The 4th and 5th gears in (some) trannys are this way, for reasons explained below.

The gear ratio has the effect of changing the rpm and torque output of a system. If you have a gear ratio of 3.92 then the torque applied to the drive gear (pinion gear) is multiplied by the gear ratio, so the output of the driven gear (ring gear in a rear axle) is modified. But the rpm of the system is also modified. The rpm of the drive gear is DIVIDED by the gear ratio.

For example. Lets say the torque output of an engine is driven through the transmission in 3rd gear (which is 1:1 or no change in torque or output due to the transmission). The engine creates 100lbft of torque at 2000rpm and is held at this rpm. The driveshaft would be spinning at 2000rpm, therefore the pinion gear would be spinning at 2000rpm. The torque applied to the pinion gear would be 100lbft.

If the gear ratio of the rear end is 3.92:1, then we would multiply the input torque (100lbft) by 3.92 to get 392lbft of torque at the tires. However the rpm of the tires would also be different. If you take the input rpm of 2000rpms and DIVIDE it by 3.92, then this would be the rpm of the tires (2000/3.92 = 510rpm).

The gears in a rear axle DO NOT make more power. They simply modify the torque output and RPMs at the tires at any given engine speed. Horsepower is simply torque*rpm. If you increase torque by 3.92, and divide the rpm by 3.92 you will end up with the same horsepower (at a given rpm).

What the gear ratio can do is modify where the engine rpm is with respect to any given speed.

With a 3.92 ratio the engine will be spinning at a higher rpm (and making more torque) with respect to a 3.55 ratio. The same is said for a 4.56 ratio.

Doing the math for "our engine (HEMI), with our transmission (545RFE)" in first gear and the different rear axle gear ratios will show the difference. I will assume a 245/70/r17 tire (30.5" diameter).

Engine rpm assumed to be 3000rpm (torque at 3000rpm is ~340 lbft).

First gear ratio is 3:1

3.55 gear ratio

Engine rpm * 1/trans ratio * 1/rear axle ratio = Tire rpm

Engine torque * trans ratio * rear axle ratio = Torque output at tires

Therefore

RPMS: 3000 * 1/3 * 1/3.55 = 282rpm at the tire (~26 mph)

TORQUE: 340 * 3 * 3.55 = 3621 lbft

3.92 gear ratio

RPMS: 3000 * 1/3 * 1/3.92 = 255 rpm at the tire (~23 mph)

TORQUE: 340 * 3 * 3.92 = 3998 lbft

4.56 gear ratio

RPMS: 3000 * 1/3 * 1/4.56 = 219 rpm at the tire (~20 mph)

TORQUE: 340 * 3 * 4.56 = 4651 lbft

RPM vs Gear vs Speed

Turn Signal Cancel operation: three things have to be "true" for the signal to auto-cancel after activation: