3.23 or 3.73

[katie]

I am looking to buy a 2007 Classic Chevy Silverado. My question is what is the difference between a 3.23 and 3.73 ratio? Which one do I want.

[Moostang]

With a higher gear ration you hit your RPM's faster. When I used to drag race (mustang) I went from a 2.73 to 3.55 to get the RPM's up faster for more speed. Of course that meant I was shifting faster and gas mileage wasn't as good. Plus I think you lose more top end. What are you plans with your truck?

[75K30]

I do not wish to contradict Moostang here, but I do wish to clarify a few misconceptions about gears and ratios.
The lower the gear, the higher the ratio. Super low gears are numbered in a very beg ratio. IE 5.13's are lower (numerically higher) than a 3.23:1.
This is simply the ampunt of revolutions required to turn the wheel i recilution. A set of 5.13's will require 5.13 revolutions of the driveshaft to turn the wheel one revolution. The tire has an effect on how far the tire will travel during one revolution. A short tire will not travel as far as a taller one, and will effectively take gear away. This is part of the reason why tall off road tires need extra gear to help keep the engine at the proper rpm.
Now as far as speed goes, it is a misconception that top end speed will be sacrificed with lower gears. Speed is directly proportional to hp. An engine is only capable of a given speed when resistance factors are considered, The change of gears will not change the top speed, it will only change the engine rpm at the same speed. If an engine only makes a couple of hundred hp. it may only ever see a top speed of 120 mph with super high gears,and about the same with low ones. Super low gears will just spin the engine at a higher rpm, but the speeds will be about the same. The lower gears will accelerate at a faster rate and can get up to speed much quicker.
Lower gears are a better choice for hauling / towing, because the advantage obtained by lower gears help maximize the torque output of the engine, and the engine will not have to work as hard to get things going. With modern overdrive transmissions the ability to run a lower rear axle ratio is optimized by the use of overdrive, so you can get the benifits of the lower gears for acceleration, and the lower highway rpm associated with overdrive, and freeway speeds.
Katie, getting to your question, now that I have confused everyone. The 3.23 gears will not accelerate or tow as well as the 3.73's will, so if you are going to load your truck down you may want the lower gear (3.73).
The difference in gas mileage is minimal.
Tire size will play a big role in the equation. If you plan on running larger tires in the future, you will need the lower gears.
Hope this helps a little.

[Moostang]

Wouldn't you still possibly lost top speed because you are hitting the higher RPM's so you are likely to redline a lot faster?

[Moostang]

Ohh don't forget you are going to have to have your speedo recalibrated (probably through the computer)

[75K30]

Sabrina:
The gears would have to be terribly low in order to reach an rpm so high that the vehicle would eventually stop accelerating. Drag from rolling resistance and air will provide enough resistance to prevent this from happening. In most cases the engine does not make enough horsepower or torque to make this happen. Cam profiles for the dtreet just do not work well at these rpm's which will make them a poor choice to make this happen.
If we could gear to run an unlimited mile an hour, we would never need larger displacement engines, but we know this to not be true, we are limited to a reasonable speed, and this is due to horsepower, and not gears.
Take your drag car as an example, if you still have some time slips from before and after you changed the gears, you will find the speed stayed within a mile an hour or two. The real change was to the E.T. The 60 foot times would have decreased and this would net a better overall E.T., but the miles per hour remained relatively unaffected. You could have changed the gears to 4.88's and run the same mile per hour, just at a higher rpm, and the E.T's would have been better. Now the limiting factor would have been the engine, it may not rev high enough to run that much gear, but the miles per hour would be the same, and with lower gears it might just reach the maximum miles per hour much quicker.

[daman]

Originally Posted by katie

I am looking to buy a 2007 Classic Chevy Silverado. My question is what is the difference between a 3.23 and 3.73 ratio? Which one do I want.

If you plan on doing any towing go with the 73 if not the 23 will work.
towing with a 23 will suck the gas bad.

if i was buying this truck the 73 is what i would get hands down.