Lowmiles

iTrader: (3)

Thinking about swapping my gear to a 3.9 or 3.73. Was how much of a difference the 3.9 would make vs a 3.73. I plan on running a 28" bias ply on the track and a 305/35-18 on the street. And don't want the car wound up too much. Drive ability isn't too much of a concern, this is mostly a toy, but I do take it on 2 hour trips sometimes.

CNB

iTrader: (4)

Its personal preference. I ran 3.90s and now have 3.73s. I prefer the 3.73 for the street!

Lowmiles

iTrader: (3)

My main concern is will the car be wound up on the hwy with a 3.90.

SNLPerformance

iTrader: (15)

There's about a 100rpm difference in cruising between the two, this link will help show the little difference...
http://www.f-body.org/gears/

Spectre86

iTrader: (42)

Keep in mind the z06 has a mn12 trans vs the mn6 in the normal C5s. I believe gears 1-3 and 5-6 are shorter.

Lowmiles

iTrader: (3)

Yea I did the calculator, but I unfortunately can't find a 28" bias ply that will fit my 17" dark stars and is DOT approved. So I think I'm going to go with a 3.73 and a 26" bias ply with a 305/40-18 (or something close) for my street tire.

Unless I can find a Drag radial that will work just as good as bias plies, if I can then I'll go to a 3.90. I'm really just trying to shorten the gearing a little for 1-4 at the drag strip, right now I have virtually no use of 4th I cross the 1/4 mark at around 4900 rpms.

alans02z

iTrader: (9)

I have 3.90s with my procharged z. I love it. I run a 26 Et street on the track and 305 555's on the street. I drive it all over. Get 26 mpg on the interstate. Yeah, you have to be on top of it when you start going through the gears but thats why they sell shift lights.

Lowmiles

iTrader: (3)

How is it on the hwy? Are you running 305/35s or 305/40s on the street? And what do you go through the 1/4 at?

alans02z

iTrader: (9)

I run 305 35s and on the hwy its just fine. No issues at all. I dont have 1/4 track close here, but the P/O went 134 on a 26 Et street and less power. Growth on the big end with a bias ply helps at the track. Im sure before long I would need a taller tire, but I may get to a 1/4 track maybe once a year so I dont worry about it. Its all 1/8th around here.

Lowmiles

iTrader: (3)

I'm doing a h/c/i set up in my car. Shouldn't trap more that 128, but may put a 150 shot later on so I want to make sure I'll have some gear left for that.

HioSSilver

iTrader: (8)

I have 3.90's op. I also run a 26" dr. I find them to be a great match for the bolt-on ls6. I go threw the traps at about 6600-6800 with them.


I think 3.73 would be good also. Your splitting hairs as neither will make or break your car.

redbird555

iTrader: (14)

Keep in mind that the c5z uses the 2.97 mn12 gear set so 3.90s will be VERY short. Having that gear set with 3.42's is like having 3.90s in the fbody 2.66 mn6 gear set. I would go 3.73 if anything

Lowmiles

iTrader: (3)

Crossing the traps at 6600-6800 is not good for what I want then. I want some room in rpms, I do intend to put a shot but not sure how big yet. I just want to make sure I pick a gear that will leave room for the shot. As of now I have virtually no use of 4th gear, I cross the traps at around 4900-5100. So I want to get a big more use out of 4th and still have room to not need 5th when the shot goes in.

HioSSilver

iTrader: (8)

I know....but that would really yank with a good tire.
I am over 130 on the traps. How fast do you plan on trapping? You said you may use a 28" tire. That would work with the 3.90's if you sprayed it. If you're gonna run a 26" tire and spray it then 3.73's.

Lowmiles

iTrader: (3)

I can't get a 28" dot bias ply for a 17" wheel.

HioSSilver

iTrader: (8)

Sounds like 3.73's are it then bud.

Lowmiles

iTrader: (3)

I plan to trap between 125-130 all motor and 135-140 on the spray, so may just go 3.73. But I'm thinking about just putting my dark stars on my z28 and finding a set of 16" ccws for the vette

GARY2004Z06

A 28" tire will be too tall for your application even with spray. The 26x11.50x17 ET Streets are good tires capable of producing mid 1.4s. The DRs will work but are much less consistent, harder on the drivetrain, and do not recover as well as a bias ply tire. As for gearing, we used 4.10s in the C5Z and trapped 126+ mph. I would not take issue with 80 mph and 2,400 rpm at 6th gear but that is a personal choice.

GARY2004Z06

Just saw your new post after I hit submit. LOL
If you plan on building the motor, you may wish to opt for rod bolts.
Just a thought.

Lowmiles

iTrader: (3)

No just heads and cam set up.