I'm on my iPhone BB so I'm limited to an extent. In my truck I went from 3.90's to 4.56's. I went up 1 mpg (at least) in town which is right near 6.7%. This is exactly what I was told it did for everyone that did the switch before me. I know there is a lot of info on the net about this, I just can't do an effective search right now. It sounds like you are hung up on engine revolutios vs speed, I know that's the wrong thing to be looking at.

 

i made a post about modifying the FD ratios a while back, but at that time there were no options for the G37...has this changed? I know the Z guys have been swapping their FDs to get better acceleration...even the 5AT guys were going 3.3 to 3.5 to 3.9....

 

When you get an opportunity, please enlighten me so I won't be dumb for the rest of my life. Give ma a link or anything where I can educate myself. No hurry.

 

So I did a quick google search of lower gear vs mpg. There is a lot of reading on just that one search. Here are a couple links before I just decided to tell you the search. You have to be careful when reading because some people confuse the low vs high gear.

After reading a lot more (might not be in the links below) it comes down to engine loading and not rpm. If I ever find "the perfect" article with the physics explained, I'll send it to you.

Do after market gears help your MPG? - Yahoo! Answers

http://dodgeforum.com/forum/3rd-gen-...-56-gears.html

Lower Gearing vs. MPG - Jeep Cherokee Forum

 

First link.. First Paragraph, there's your answer lol

 

That's exactly what I was trying to tell you to be careful with. He's confusing a "lower gear" with the lower numerical number, that's his first mistake. Then he goes on to say "will always provide better gas milage", and that's mistake number two. That's when you know to skip the rest because he's not providing a correct response. A couple more posts down is a guy who knows what he's talking about. I'll let you decide.

Actually, that entire link sucked! Why did I post that? There was only one guy on there that posted anything of merit. I'm going to bed.

 

What about the speedometer?
Anyone know how to make sure the reading stays accurate if you swap gears?

 

You'll need to have it recalibrated.

 

In my Dart, I went from 2.90 gears to 3.93 gears.


Holy shiat is all I can say.

 

Right, but how?

 

You can adjust the speedometer in the diagnostic settings of the car. I think.

 

3.90's or 4.10's would be sweet in these cars. Especially with a 7500rpm redline. And considering these cars make all their power in the higher rpm range it would work to our advantage to keep it in that RPM range through the gears.

 

I could easily see how a lower gear would help gain mileage in stop and go. Think of a 10spd bike. You set the gears up on the physically largest (lowest ratio) and it's very easy to get moving from a stop. Now go and put the chain on the physically smallest gear (highest ratio) and it's much more difficult to get moving from a stop. Same thing applies with the car. The lower gears will help in the city where you are having to accelerate the mass of the car from a dead stop. Once your on the freeway the gears will hurt you due to increased RPM.

 

You do realize that the different ratio gears in the transmission are having much more of an effect on this than the rear end gear is, right? The car isn't going to lug at low speeds because you put in a lower rear end gear ratio. Unless you are starting from a stop in 3rd or 4th gear.

 

4.08 is what the guys have been doing on the 350z and G35. Go over to the370z and search final drive, huge thread about it.

Btw stop arguing about mileage, its gay, especially when you guys redline your car from light to light....