Jeremy Clarkson

I have 2 questions. First why would somebody want to upgrade the diff in an S? I know they are "glass" and people have had issues blowing them, but the issue seems to be more for someone who use sticky racing rubber. I don't autocross (yet) so is there a purpose of upgrading the diff? Will you feel a difference in real world driving?

Why change your final drive ratio? I hear that lot of people go for 4:3:3... something. My question, again, is why? How will it effect the car?

Manga_Spawn

The glass issue isn't just from using sticky tires but when you are putting down a lot of power with a turbo or supercharger the trans and diff become the weak points because they were never designed to handle that power. Most people just keep adding power until something breaks and then upgrade whatever brakes.

With the final drive I am not quite so sure. I think it helps with acceleration? This is really one I don't quite understand myself but I believe it has to do with changing how the car accelerates.

S2KIrishman

yes, changing the final drive increases either acceleration, or top speed depending on the gear used...higher gear ratio will yield quicker acceleration, but will lower overall top speed...a lower gear ratio will increase top speed, but accleration will not be as quick...example, most NA guys go 4.56 or 4.77 for quicker accleration while FI guys usually go 4.3 or 3.9 to benefit from staying in boost longer

Jeremy Clarkson

I hear of a lot of people using 4.77, what exactly does that mean? What kind of gains in acceleration are we talking about? Is there a down side to it?

raymo19

It's the ratio between the prop shaft and the rear wheels. With a 4.77 the prop shaft rotates 4.77 times to rotate the rear wheel once.

Jeremy Clarkson

So what's the downside? There has to be a reason that Honda didn't put in a 4.77 in the factory if it just makes your car accelerate quicker, right?

S2KIrishman

i already stated it but, the "downside" would be a lower top speed...so that means at cruising speeds youre going to be at a significantly higher RPM for the gear youre in, which would affect gas mileage...i dont really look at it as a downside if you can live with spinning 5,000 rpms at 75mph, but the speed limit on the highways where i live are 55mph so it wouldnt really be an issue for me

Moddiction

Drive on the highway at your normal speeds but instead of being in 6th put it in 5th. That's about how it will be with 4.77's. not quite as high but very close. About 800 rpm difference. Doing the gear swap does not strengthen your diff. That is just to change the gearing. For a stronger diff there are other options out there such as puddy diffs or a few other rear end conversions.

Jeremy Clarkson

Gas mileage...right. How has your gas mileage been effected?


So what kind of acceleration gains would you see if a 4.77?

Moddiction

First couple gears or around town it feels a little quicker. Highway speeds it feels slower. Have to shift too often. Not a huge difference in acceleration at all. Just a but peppier around town is the best gain from the gears.