School me on rear end ratios and power

[wsutard1]

Ok, assuming all of our stock HEMIs make the same power how does rear end gear ratio play into putting all that power down?

For instance does the 3.21 put less power on the ground than the 3.92? Or just less torque?

Or does the gear ratio not have anything to do with that and does it only control the engine rpm at certain speeds?

 

[tjfdesmo]

Basically, it is torque multiplication. A lower(higher numerical)ratio is like a longer lever to move a load. Pull with XX lbs of force on a box wrench, then pull with equal force on a 30" breaker bar. More work with same effort(input).

 

[Statcher1]

Basically, it is torque multiplication. A lower(higher numerical)ratio is like a longer lever to move a load. Pull with XX lbs of force on a box wrench, then pull with equal force on a 30" breaker bar. More work with same effort(input).

Bingo. The man has it right.

 

[wsutard1]

OK, so more torque is making it to the ground. Which is what I thought but wasn't entirely sure.

 

[Drummin4jc]

Basically, it is torque multiplication. A lower(higher numerical)ratio is like a longer lever to move a load. Pull with XX lbs of force on a box wrench, then pull with equal force on a 30" breaker bar. More work with same effort(input).

Used to get into these a lot when I sold Peterbilt trucks.... and you are spot on! A lot of the guys working in the gas industry went with 4.10 ratio's and the over-the-road guys did 3.70 or 3.42....

Adam

 

[Kotta390]

OK, so more torque is making it to the ground. Which is what I thought but wasn't entirely sure.

It's not that more torque makes it to the ground. It's more like the same power being put down but just a lot less effort from the engine to do so. Think of a multi speed bicycle. You can apply a certain force in a higher gear and yield "x" results, but if you apply the same amount of force in a lower gear it is much easier to accelerate. Effectively going to a lower gear ratio, (numerically higher), will yield you in better acceleration and will also reduce your top mph.