In short, torque is what accelerates a car (torque is multiplied by gears and then changed to force through the rotation of the tires. Force=Mass*Acceleration).

Horsepower comes into play because it will determine how fast a car at a certain speed will accelerate.

For example if you have a 3500 lb car with 13" (radius) tires, rear gear of 4.10, and tranny gears of (2.66, 1.78, 1.30, 1.00, .74, .50).

Lets say the engine produced 300 TQ at 4700 rpm and 400 TQ at 3432 rpm. From a 50 mph roll in order to determine acceleration we could find the torque at the specific rpm and gear OR we could just use HP.

TQ way: (from a 50 mph roll)
In 2nd gear the engine is at 4700rpm and the TQ is multiplied by (4.10 x 1.78 x 300=2189.4 lbs*ft) The force produced due to the tires would be 2189.4/(13/12)=2020.98 lbs force. This would produce 2020.98/3500=.5774 g's acceleration.

In 3rd gear (much higher TQ) the engine is at 3432 rpm and 400 TQ. (4.10 x 1.30 x 400=2132 lbs*ft) 2132/(13/12)=1968 lbs. 1968/3500=.5623 g's.

As you can see this took alot of work and required we know the ratios for all the gears and the specific TQ curves.

HP way:
Acceleration can be calculated knowing ONLY the HP and the MPH.

HP*constant/MPH= Acceleration (in g's) Constant = .10754

Try it out, it works. This just proves WHY horsepower is important. If you argue RWTQ (FWHP mutliplied by gears) is more important, then you are wasting your breath.... HP and RWTQ are directly related, HP is just a nicer format to use.

 

So, after all of this discussion, have we decided theoretically which gear is the all around best gear? I know it would change dependent on where your power is in the RPM band. But on a mild street car, it nearly sounds as if my 2.73 gears are better than anyone gives the credit.

Michael

 

NO, 2.73's just suck all together. Only benefit is gas mileage as I see it. You wont ever max out 3.42 gears, or even 3.73's for that matter.

And I gaurantee you a 4.10 M6 car will pull on you from any speed, ANY.

 

I guess I am just stuck with my 273s? Everytime I search old posts or read new ones on "best gears for an auto" I leave more confused than when I started looking? So this is why after having the car for some years now, I still run the 273s that I hate! I just will never know what to upgrade to and cant afford to go with 342s and then switch to 373s if I need to??????

You guys keep debating and at some point we will all have an answer!

 

To answer this post, yes a 3.73 will usually pull harder at all speeds.......unless you are in the dead spots.....which can't be avoided with any gear. But do you want to be running 2800rpm on the freeway and putting all that extra strain on every part of your car?

I'm going 3.42 and doing the rest with HP

 

Honestly I argue all day that higher gears are faster at any speed, but im still running stock 3.42 gears because I dont think gears are worth it. I have traction problems as it is and i do too much HW driving. So if i were you i would either get more speed from HP, or I would go with 3.42's tops. I think higher gears are only really suited for a track, not the street.

But why cant GM just make the gears rediculiously steep and have a 6th that would be normal. It would be the best of both worlds.

Like 3.42 rear and (3.2, 2.14,1.56,1.2,.84,.5) on the 6-speed. 1-5 gears would be exactly like 4.10's and 6th would be the same as normal. It would get badass acceleration and badass mileage.

But GM doesnt think like that, oh well.

 

This is the way I would look at it:

Examples previous shows in a race situation while going through multiple gears, a lower numerically geared car could out accelerate a higher numerically geared car based on short shifts to transmission gears that provide less multiplication.

However, look at the torque produced by each gear separately. Compare torque multiplication in first gear for a 3.42 to first gear for a 2.72 at all speeds/rpms. Then second gear and so on. The 3.42 will always have higher torque multiplication. This is what gives the feeling of more punch when driving with numerically higher gears.

I believe that is what most of us wants anyway. It may not be faster overall, but it will feel faster in individual gears.

Michael

 

WOW! I cant believe I read this whole thread! ....I went from 2.73 to 3.42 and Im a happy camper. I wouldnt want to be hittin close to 3000 in 4th on the highway. Im ok with 2400

 

THIS IS THE BEST THREAD EVER! I LEARNED A LOT HERE. ANOTHER HAPPY CUSTOMER WITH 3.42

 

So as the original poster asked, his 3.23's are good overall unless he has traction in 1st to use the 3.73's, right? Wow what alot of reading, but what good learning.

-Dustin-

 

wow this thread was brought from the dead lol

 

Ya, well I was wondering the same question. I am stuck between a stall and moving from 3.23's to 3.73's and am just trying to determine which is better for me. I have my own thread on it but found this in my searches. Just wondering the exact advantages and if my 3.23's will do fine.

-Dustin-

 

I started with 2.73's then went to 3.42's then 3.73.
3.73 definately pulls harder in all the gears.
The car cries out "Do Me! Make me accelerate!"
all the time, even over the 3.42's
However nice, the 3.73s makes the A4 car feel like it needs a 5th gear for highway driving.
I added a Gearvendors OD unit that makes the 3.73 into 2.91, but if I wasn't able to do that I'd go with the 3.42's.

 

So this thread made me buy 3.73s, have 3.42 now.

Anyone know a good place in Tampa to get them installed, other than Ramseys (not that they are bad just a PITA to get to)? Search only found Orlando info, not Tampa. I am new to the area and miss the quality mechanics in NY/NJ already.

 

stereodan the link doesnt work. i would like to have both the a4 and m6 spredsheet