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Old 12-02-2007, 01:23 AM   #1
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Default Have 3:42 gears thinking of going to 3:90 need imput?

What can I expect if I change gears?

thnks Mike
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Old 12-02-2007, 09:28 AM   #2
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I got a lot more wheel spin (first & second useless on the street), about 2 mpg loss in mileage but all great at the track. I seemed to have picked up about .30 in the quarter mile (my sixty foot went from 1.64 to 1.489). I have had to hit the brakes before busting the 11.5 rule recently. Best new run was 11.52 at 91 mph (hit the brakes real hard at the end). Hope to run a complete run next Saturday. Pit-man
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Old 12-02-2007, 10:50 AM   #3
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Default Do it!

Yea , I think you should do it, So then you can sell me your 3:42s!

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Old 12-02-2007, 08:10 PM   #4
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If you have a cam you will swear the car should have came with 3.90s. It works great for everyday driving, and my local road course the car is fast out of the turns.
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Old 12-03-2007, 02:28 AM   #5
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3.90's are great but you need some meat out back to help stick 1st and 2nd!
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Old 12-03-2007, 05:11 AM   #6
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^ Lol, I just put some street tires on my FRC (wore out the Nitto DR's) and I can spin the damn tires in 5th S0 needless to say I just ordered some new DR's and my street tires are practically new

99FRC...I dont know from personal experience, but I have heard the 3.90's are pretty sweet. Personally I've always liked stock gearing in all my cars, im more of a highway hunter so to speak.
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Old 12-03-2007, 11:15 PM   #7
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I was told the 3:90's will be the equivalent to the gearing in a C5 Z06 trannie.
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Old 12-04-2007, 12:12 AM   #8
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I just put 4.10's in my Z06 and love them. I say go for the gears!
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Old 12-04-2007, 09:13 AM   #9
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Quote:
Originally Posted by 99FRCTorchRed View Post
I was told the 3:90's will be the equivalent to the gearing in a C5 Z06 trannie.
Nope. The C5 ZO6 has 3.42:1 gears as does the C6.

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Old 12-04-2007, 11:16 AM   #10
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Quote:
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I was told the 3:90's will be the equivalent to the gearing in a C5 Z06 trannie.
4th gear will be different, but final drive on all other forward gears will be the same. I hope to get 4.10's for mine soon.

(currently stock 3.42's in an FRC)
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Old 12-04-2007, 11:45 AM   #11
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Quote:
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Nope. The C5 ZO6 has 3.42:1 gears as does the C6.

Keith
hes talking about the steeper gearing from 1-3 gear. basically it makes a normal C5 act like a Z06 gearing wise from 1-3 but it will have a gearing advantage once both hit 4th.


do you guys like 3.90's in your Z's??? i am leery going with a steeper gear in the rear with already steep trans gearing. is it worth it?
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Old 12-04-2007, 01:27 PM   #12
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do you guys like 3.90's in your Z's??? i am leery going with a steeper gear in the rear with already steep trans gearing. is it worth it?
I really like it and would not go back to the 3.42s. I am making close to 500 rwhp and 475 rwtq with my 383 stroker right now and I still love the 3.90s in the back. The car was meant to be with those gears. They make even leisure cruising in the Z fun. I know I can break the tires loose when I want to or just putt around.
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Old 12-04-2007, 05:19 PM   #13
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I really like it and would not go back to the 3.42s. I am making close to 500 rwhp and 475 rwtq with my 383 stroker right now and I still love the 3.90s in the back. The car was meant to be with those gears. They make even leisure cruising in the Z fun. I know I can break the tires loose when I want to or just putt around.
Most of that Id bet is due to HP not gearing No?
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Old 12-04-2007, 05:52 PM   #14
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I have 3:90's and all I can say is they are awsome.... It takes a little more effort to launch and not break the tires lose but love it anyways.... 80mph on the highway 2500 RPM... No more 200mph runs though )-:
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Old 12-04-2007, 05:55 PM   #15
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I went from 3.42's to 3.90's last spring. Over the summer with my Goodyear GS-D3's, they were hard to break loose from a roll. Now that its cold (car is away now) they break loose easily in 1st and 2nd. I have 396 hp. In the spring I am doing new heads and a different cam so I am sure that breaking them loose in hot weather will not be an issue. The only thing I can add is I wish I put them in a long time ago. 6th gear on the highway is much better, 3rd gear will pin you in the seat, 2nd gear is holy crap time and 1st is usually when the wife begins the scream. She is usually out of breath by third though
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Old 12-04-2007, 08:17 PM   #16
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Quote:
Originally Posted by BitViper View Post
Most of that Id bet is due to HP not gearing No?
It is due to the gearing. My direct comparison was when I put them in the car and went from the 3.42s. That happened with my H/C 452 rwhp.
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Old 12-05-2007, 12:03 AM   #17
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Made the decision to get the 3.90's put my deposit down this morning being installed a week from Saturday. The work is being done by Rick at Synergy.
Can't wait
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Old 12-05-2007, 03:53 AM   #18
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Well keep us posted. I will have to go to LB one of these days and meet up with you. Well once I get it up and running again Lol, my clutch is slipping pretty bad so I ordered a Mcleod Twin Disk, so in a couple weeks when it comes in it will be back on the road, so in the meantime I have to drive the Z06 (LOL)
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Old 12-05-2007, 07:08 AM   #19
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Good choice I went to a 3.90 a few months ago and definately think any one should do it. Unless over like 700 whp!
I have 2 in car videos below before and after they are not exactly from the same start and stop points but you kind of get the idea

3.42 30-105 run


3.90 20-130 run
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Old 12-05-2007, 07:28 PM   #20
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YOU SHOULD WAIT ON THE GEARS UNTIL YOU GET THE CLUTCH>... Save money on isntall...

I am pretty sure.... For the gears they have to drop the whole tq tube assembly and will have to do it all over again for the clutch.... Might save you some money to do it all at once with the car already apart. (-:
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