JUIC3D

Hey all,
I'm looking to beef up the rear end and change the gear ratio in my 2008 LS3 and I'm looking for clarification on a gear choice from the community.

The car currently makes 517whp on motor and I might be adding nitrous in the next 12 months or so. I cross the 1/4 mile at around 5400 right but I spin the motor to 7,000. Details of the car are in my sig.

I'm thinking 3.90s might be the best bet as this calculator puts me at around 6700 at 132mph and should leave room for more if I decide to spray down the road. I could also switch to a taller tire as I currently run a 275/40-17.

http://mysite.verizon.net/foofoo2/c6/MN6-Z51-4.10.html

Thoughts, advice, and opinions are welcome

Thanks

superscout03

I went with 4.10 and do not regret it at all, If you dont live at the track and want to make 6th gear useable I highly recommend the 4.10
Not to mention the 4.10 just makes everything so much more responsive and provides me with that low end grunt I love compared to the stock 3.42 gear, especially if your running a big cam the gears really help.

JUIC3D

I guess I could elaborate more on the use of the car.

I race it pretty much every weekend I can and it is my daily driver.

4.10s put my rpms almost at redline in 4th gear on the motor. With nitrous, I think the 3.90s would give me more room. I'm kinda leaning towards them but wanted input from the community.

BluV

I would agree with you based on your rpm at the line and future intentions. The 4.10 would be great now but won't leave much room for further changes - unless the change would be so huge that the 3.90 would entail another gear shift before the traps as well, in which case it won't matter anyway.

Joe_G

I've had both 3.90 and 4.10's.

Get the 4.10's. I dropped .05 or more consistently in my 60 foots with the 4.10's. They are surprisingly easier to launch. And as you know the gears help the clutch live.

You will not max them out N/A - not even in the winter. Tires grow a little at speed.

If you don't believe me ask the ls2 record holder, Andrew (dsp300c).

If you start shooting nitrous, get taller tires, and at that point, you'll want to get bias ply anyway as your rear end will be at huge risk with a 150 shot on drag radials.

PRAY

Wow, it's like Desavue (sp). I think Joe G and I share a brain. Everything he said is right on the money. Should be the first mod in any Vette IMHO. 4.10's all the way bro. Just run a taller tire for the nitrous at the track. You will need the bias ply at those numbers anyway to save the rear and actually get traction unless you are going to invest in the rest of the suspension. Almost all street encounters from a dig will be over by 130 anyway. Heck, most roll runs are over by 130 if you are winning.

p.s. We sell rear ends.

JUIC3D

Rear end is already in the works Brett-hence this thread. It's looking like I'll be doing the clutch and the rear end at the same time.
Cajun was saying 3.90s and that I should ask your opinion.

Joe what rpm do you cross in 4th? I feel like I wouldn't lose all that much 3.90 to 4.10 and would have room to grow, is that not correct? I don't want to spin it over 7000

Are your tires the same height as my 275/40-17s?

Pardon my ignorance but I just want to learn

JUIC3D

Joe, is your Z51 the same gearing as mine? I assume so but I know the transmissions are different.

Shoaf85

I have 3.90 and love it! I knew I would be gunning for more power down the road so I didnt want to have to run with a taller tire or change to 5th! IMO 3.90 but thats me! If you dont plan on making more power than 4.10 for sure...but we all know how that goes!

Joe_G

I don't know exactly where I cross the line, but I rev it to redline most of the time in my scans. I know I never hit it before the line at all.

My tranny is the same ratios as yours Justin and my tires are the same height.

I didn't think it would be much of a difference 3.90 to 4.10 but I was pleasantly surprised.

You want to gear your car for redline at the stripe. Anything short of that is leaving ET on the table.

If you plan to race 1/8 mile...3.90's are better as 4.10's require a shift to 4th before the 1/8 mile line.

Kerrdogg

Engine NA

3.90 w/ 25.7 tall tire @ 130mph = 6657 rpm
4.10 w/ 25.7 tall tire @ 130mph = 6971 rpm

Spray

3.90 w/ 26.0 tall tire @ 142mph = 7160 rpm

3.90 w/ 28.0 tall tire @ 142mph = 6648 rpm
4.10 w/ 28.0 tall tire @ 142mph = 6989 rpm

Guess it depends on what rpm you want in the traps.

JUIC3D

Thanks Joe. I'll go with the 4.10s then.
John, does that have anything to do with transmission ratios? I guess it really doesn't matter because 4th is a 1:1 ratio anyway so that doesn't matter.

dennis50nj

your car might fly with gears, if you ask c6devil 390, if you ask spinmonster 410, if you look around some guys do great with 342, yourself for one, fartpipe for another, if you go with nitrous you don't need gears, yes you can put taller tires, but that adds weight, 410s have smaller and more teeth, easier to break, the taller tire more weight is more stress on those smaller teeth, your 275 40 17 is great hooking and light, with nitrous you will hit redline real quick in each gear, and the tq will be very destructive on those small teeth, but you will never know until you try

Kerrdogg

4th is 4th

If you are really thinking of spraying I would probably leave it alone, the spray will love the 3.42's, your connecting rods won't... Then you are talking to a guy with a race car with 3.27's and who used to love 2.73's so I could down shift into first from a roll on the street....

JUIC3D

I'm not spraying the car w/o a built rear and I'm not going through the trouble of building the rear to keep the stock gear ratio in it

Nitrous is on the backburner--very back. I'm absolutely more concerned with NA performance than I am with nitrous.

My car will always be a N/A car and I'll treat it as such.
It will never be a nitrous car such that if the bottle is empty, I don't have any performance.

dennis50nj

of-course! I'm just saying 342S are stronger, built rear or not, i would go 410s