Need Advice On Gear Choice, Please Help!!

1

13 GT/CS

Member

Jul 5, 2013

36

3

9

Oct 5, 2013

#1

• Oct 5, 2013

• #1

My current setup is a 2013 Automatic GT and its a daily driver.
I am looking into getting a supercharger in the future as well but I need some advice on gear choice.
It came stock with 3.15..but I cant decide if I should go with 3.55 or 3.73. 4.10s i think are out of the question because i have heard of MPG loss and I cant afford that. All responses are appreciated and look forward to reading them, Thanks!!

 

Husky44

10 Year Member

Sep 27, 2006

865

104

74

Tacoma, WA

Oct 5, 2013

#2

• Oct 5, 2013

• #2

We can help you more if you tell us what you're trying to accomplish. Are you building a 1/4 mile car? Daily driver, with lots of highway commute miles? Stop-light terror?

FWIW, there's charts out there where you can put in your gear ratio, rear tire diameter, trans gearing, etc, and it'll spit out what your RPM readings will be at various speeds for each gear. IMHO, there's not a huge amount of difference between 3.55s and 3.73s. I'd go with the 3.73s, unless you're going to be racking up huge highway miles, and aren't as interested in street performance. I'm running 3.73s in mine with a blower, but it's a manual. Very happy with it; still well-behaved on the highway, and can net me better than 24 mpg if I drive like a nun.

 

1

13 GT/CS

Member

Jul 5, 2013

36

3

9

Oct 5, 2013

#3

• Oct 5, 2013

• #3

Husky44 said:

We can help you more if you tell us what you're trying to accomplish. Are you building a 1/4 mile car? Daily driver, with lots of highway commute miles? Stop-light terror?

FWIW, there's charts out there where you can put in your gear ratio, rear tire diameter, trans gearing, etc, and it'll spit out what your RPM readings will be at various speeds for each gear. IMHO, there's not a huge amount of difference between 3.55s and 3.73s. I'd go with the 3.73s, unless you're going to be racking up huge highway miles, and aren't as interested in street performance. I'm running 3.73s in mine with a blower, but it's a manual. Very happy with it; still well-behaved on the highway, and can net me better than 24 mpg if I drive like a nun.

Click to expand...

It is a daily driver, but I would like to take it to the track on the weekends as well. Smoking some people at stoplights wouldn't be bad either. My current setup has BBK longtube headers/Off-Road Xpipe, Boss Manifold etc (but that would be removed probably next summer when I invest in a Super Charger. I hear a lot of people recommend 3.73s but I was reading somewhere about 3.55 being good for SC applications. Gears is one thing I know not much about so im clueless in the subject. Just don't want to invest and the be disappointed.

 

TheShabz

Member

Aug 4, 2012

275

18

19

Los Angeles

Oct 10, 2013

#4

• Oct 10, 2013

• #4

I'm in a similar spot with the gears with an automagic and blower in mind. I'm sure anything more than the 3.15s we have now will be great, and I don't have too many concerns over the mileage. For me, it's getting in the sweet spot for the weekend 1/4mi and canyon roads

 

Dugl

Member

May 18, 2011

83

16

19

PA.

Oct 11, 2013

#5

• Oct 11, 2013

• #5

There are guys on here that are more familiar with automatics, but I believe the autos are geared lower than the 5/6 spd manuals, so you may not have to go too aggreesive. Tire diameter makes a difference also...I lost an inch going from a 55 series to a 40 and went from a 4.10 to a 4.30 effective ratio. (28" tall slicks fix that) The other thing is that I am almost positive you will need a tuner ($400) to manage shift points and speedo calibration. (my manual is off 10 mph on the highway...my GPS is spot on) I'm also not sure at what point you may need extra cooling for the trans.

 

TheShabz

Member

Aug 4, 2012

275

18

19

Los Angeles

Oct 11, 2013

#6

• Oct 11, 2013

• #6

Yea, that's the sticking point for me. the mentality for the manuals doesn't quite jive with what an auto should have. of course, a dyno tune is in the works for when this all happens, so it's not just the speedo and shift points i'd be messing with. I've heard of people putting down 600hp on the stock trans, so it seems like it's pretty sturdy as it is.

 

BackInBlack

5 Year Member

Oct 9, 2011

433

26

49

Southern California

Oct 12, 2013

#7

• Oct 12, 2013

• #7

3.73s

 

Alloy08GT

New Member

Oct 19, 2013

5

0

2

Owensboro Ky

Oct 19, 2013

#8

• Oct 19, 2013

• #8

Just put in a set of 3.73's, haven't had them long but I can tell a big difference between the 3.31's I had for sure. Yesterday I actually got sideways in 3rd with Traction Control ON...............!!!!

(And 4 people in the car I might add)

 

B

BobEFFC

New Member

Sep 8, 2013

10

1

2

Detroit

Oct 20, 2013

#9

• Oct 20, 2013

• #9

Wait a minute here.. You have a 3.15 and an 8500rpm Boss manifold and an automatic..? With that setup a 4.10 (or more).
A centri I'd still probably run a 4.10 although the 3.73 would be fine too. For a daily driver with a positive displacement blower a 3.55 is plenty of gear especially if you're concerned with gas mileage.