DTMR

Im stuck between 3.73s and 3.90s. I was leaning towards 3.90s but someone on the site stated that 4th redlines at 115. right now my 3rd redlines at 100 with my 3.31s! I also have cams and increased my redline to 6800 and will be increasing it to 7000 after I do valve springs and heads. So what will be the difference in top speed between 3.73s or 3.90s on a car that redlines at 7000 rpm

S197GT07

Research shows, most people go with the 3.73's or 4.10's over the 3.90's because the 3.90'
s are made by Motive and prone to whine.

outceltj

^^^^^^^^^^^^^^^^^^^

what he said

JCON

What size rears tires do you have? I can give you exact calculations on numbers if you give me that info.

Also, for the price and your mods, I would look at a supercharger instead of new heads. They're expensive and are a great mod but a supercharger will give you more power per dollar and your mods on the car already will be great for one. Just a thought.

DTMR

I have a manual trans with 18 wheels and 275/40 tires i dont care about whine im asking about top speed haha and i like superchargers but i want to do a fully forged bottom end first thats why im starting with the top (doing cams and heads and stuff) then doing bottom so i can safetly push high boost without worrying about stuff but thats in the future haha

JCON

First off, why does your manual have 3.31 gears? Should be 3.55 from the factory.

If you actually run it to 7k, you're going to bounce off the limiter. I would base gear selection 100 rpms below your red line. Also, what trap speed are you shooting for? What is you're ultimate goal? How deep i nto 4th gear do you want to go?

If drag racing (only racing where you really want to run at redline every shift), remember side wall is important. Additionally, if you increase side wall width (either by going with a higher percentage to tire width or getting a wider tire), thereby increasing overall diameter, you can increase the MPH each gear is capable of. Get a set of rear 18x10's and throw a 305/40 on it and you're looking at a ~4% increase in maximum MPH for each gear.


At 7,000 rpms on your current tires (numbers are in mph):

4.10's

1st - 40
2nd - 68
3rd - 96
4th - 135
5th - 188 (without major mods to every part of the car, you will not hit this)

3.90's

1st - 42
2nd - 71
3rd - 101
4th - 142
5th - 198 (without major mods to every part of the car, you will not hit this)

3.73's

1st - 44
2nd - 74
3rd - 106
4th - 149
5th - 207 (without major mods to every part of the car, you will not hit this)

3.55's

1st - 46
2nd - 78
3rd - 111
4th - 156
5th - 217 (without major mods to every part of the car, you will not hit this)

I would recommend 4.10 gears as they are for acceleration. (they make higher for the 8.8" i believe 4.30's are available from FRPP). In 4th gear, you'd need to be pushing a 9.9-low 10s 1/4 and ~600rwhp or more (many variables apply here). If you plan to top the then maybe look at 3.90's

jdmcbride

3.55s were an option in 2008 for manuals only. 3.31s were standard on both manuals and automatics.

JCON

What a terrible decision

DTMR

Wow thanks for all the information this helps alot, i dont know why the guy said it would max out so soon then. Ill prob set my rev limiter to 7100 after i install the better valve springs and heads im just trying to find the perfect ratio that will be good for track racing and drag racing like somewhere in between

JCON

http://www.hotrod.com/techarticles/g...s/viewall.html

Know the limits of stock parts. In this case, running the redline that high would likely cause cam phaser issues. I would consider Comp Cams lock out kit.