How does this work, lower numbers like 2.73 mean higher speed and higer number like 3.42 mean more acceleration or is it the opposite? Or am i completely wrong with this.

 

the higher the number, the lower the car is geared, 273s mean higher top speed, if you have 700 HP or drive in a vaccume, you dont have the power to overcome the drag.

i have 3.73s in mine there all right, i wish i had done 4.10s though

 

okay, i see, i'm putting a 350 in my camaro probably gonna put a 700r4 or t-5 i'm still debating this, it used to have a 2.8 v6, i know the gearing is probably very off in the diff, id be better off just changing the whole rear end aye? I already have stiffer springs installed in front and waiting to tear up the rear end to put some stiffer ones their too. So higher numbers do mean more power, but you lose some speed. What would be the best to go in mine, note that i can't put something that will be riding a 3500 rpm going 60mph in last gear cause i do lots of highway mileage. but i still don't want it too be bogged down like crazy, need a good balance what would you guys recoment?

 

Lower numbers do not NECESSARILY mean more speed; but they DO mean that at any given speed, the engine is turning slower. Likewise, higher numbers mean that at any given speed, the engine is turning faster.

Higher numbered ratios will create better acceleration, because the motor does a certain specific amount of work (releases a certain amount of energy, measured as torque) each time it turns. The more time it turns, the more energy comes out. At the same time, energy isn't free; in order to get more OUT (power), you have to put more power IN (fuel, and air). And, no engine can just keep speeding up indefinitely; sooner or later it reaches a point at which its torque output begins to fall off faster than RPMs increase (the peak HP RPM). It is counterproductive to try to make the motor spin faster than that RPM, because starting at that point, power output GOES DOWN instead of UP.

Same for the whole "top speed" thing. People are all about, my 305 TBI car with its 2.73 gears has a tach that goes to 6000 RPM or whatever, and I'm doing 85 mph or whatever at 3000 RPM, so that means my car will do 170 mph. WRONG. You'll see that in this post, I'm sure; lots of people with underpowered cars will come on here and tell you "I've had my car up to [insert impossible speed here]". In reality, the power (time rate of doing work, or time rate of release of energy) required to propel a car INCREASES RAPIDLY with mph, specifically, with THE CUBE of mph (i.e. to double the mph, power required goes up BY A FACTOR OF 8!!!); the car's "top speed" is that speed at which the ENGINE POWER that actually reaches the road (RW HP), as determined by the RPM that the gearing forces it to run at, EXACTLY EQUALS the power required to push the car at that speed. So, if you have a car that takes let's say 150 HP to push along at 125 mph, and you have a motor that produces 150 HP at the wheels (after all drive train losses) at 4000 RPM, and the gear ratio is such that the engine runs at 4000 RPM at 125 mph, then that's the car's top speed. It's entirely possible that if the car took 175 HP to push at 135 mph, and the engine could put 175 HP to the wheels at 5000 RPM, and you changed the gearing UPWARD (higher number) such that the engine could do 5000 RPM at 135 instead of 4000 RPM at 125, the car MIGHT ACTUALLY GO FASTER by using a higher-numbered gear.

Before just jumping to the conclusion that you should change your rear end, pop the cover off and look at what gears are in it.

The ideal gear depends on what RPM the motor is most efficient at, and what you use the car for. For a typical car with a 700 or T-5, it's usually about 3.73; except if it has TPI, which limits the RPM at which the motor can produce power, 3.23 to 3.42 is usually better.

 

Btw, if your car had a 2.8 V6 originally, you probably have either 3.23 or 3.42's in there if you still have the original rearend under it, so you should already have a good ratio. 2.73's suck in an automatic car, and they're practically unuseable in a car with a manual trans. I changed my gears from 2.73 to 3.23 in my TBI/700r4 car, and it made a huge improvement.