CuZ06

HI All,
I am considering changing the gears in my Z06, I am currently right at 460rwhp and want to swap out the 3.42s....

I am considering 3.90s but have been informed 3.73s(great resource) might be a better fit...

I wanted to solicit some feedback from my fellow forum members who might have this set-up, I have read nothing but positive results of guys/gals who have done this modification.....

Thanks for your help in advance

-Jason

DIXZ

I have a Z06 with 466 WHP. I have had 3.73's, 3.90's, and 4.10's in the car in the last year. All I can say is that I love them all, and have had alot of fun with all of them. It all depends on how you drive your car.

I prefer the canyons, the more technical the better. The 3.90's and 4.10's are my choice with the 4.10's having a little more edge.

p1bz

I have 3:90's and ???? horsepower, cars never been dyno'd. Built LS6 and 14ish lbs boost. Great setup.

CuZ06

I just secured the donor 3-rib, should get it in a week or so....now to finalize the ratio choice

Flatlander

My Z has 451 RWHP. Went with 3.90's. Awsome acceleration and makes 6th gear cruising much easier to use.

MStrahan

Another user of 3.90 gears. Never dyno'd, but given my list of mods I'd say a conservative 460rwhp. I love the gears. The car was a blast to drive before, but now I can't get enough.
I've been told 4.10 gears are just a little too much with the Zs already aggressive transmission.

CuZ06

Good Deal, I am right at 460rwhp on a nice tune from Ed Hutchings and this is the exact feedback I am looking for!

CuZ06

The diff is now at RKT and ready to start the teardown.....I am still on the fence but really want the 3.90s but I don't want to make the car useless to drive .....

I need more convincing LOL.....I am still rebuilding it but want the final push for 3.90s with the m12 and my power level

bumble-z

The 3:90 will be just fine with the gearing of the M12.

I wouldn't go any higher.
You will be some where close to 2200 RPM @ 70mph, which isn't bad.

LoneStarFRC

Listen very closely to whatever Rick recommends for you and your intended driving style or needs. He will not steer you wrong. Cereal.

Don't forget, the Z06's already have shorter transmission gears than the regular 6-speeds to start with and that can also have a major impact on your choice, plus traction issues can easily come up when your HP levels increase substantially. Personally, I would not go lower than 3.73s. You get too low and first gear can easily become useless.

Good luck.

CuZ06

Rick said the 3.73s would work(his recommendation) but I wouldn't notice much difference. He did say the 3.90s would work but to start a thread to solicit feedback on those who have done it....not one person has regretted doing this once they have...some said that 3.73s were great but regreted not getting the 3.90s.....why does it have to be this damn hard LOL.....

cdkcorvette7

You're in very very good hands with Rick.

As others have said, your choice depends on what you're looking for. You probably won't notice much of a difference going to 3.73's and no other new mods. There will be a difference but it'll be subtle.

If you go with 3.90's you'll notice a significant change (you'll feel like you just added 50 hp even though you didn't actually gain anything) but your gas mileage will suffer slightly and you're liable to need tires more frequenly

Also be sure to take your long term plans for the car into account when making your decision. Are you going to stay at your current power level or add more?

If it were me I'd go with the 3.90's but it's your car... Ask yourself if three months down the road you're still going to be happy with the mild change or wishing you'd gone with the 3.90s...

CuZ06

I think I am going to go with the 3.90s and get some stickier rubber to deal with the new gearing.....I am going to sleep on it tonight

Guys who went with the 3.90s above, what rear tire are you running? I am currently running 18x10.5s all around with 275/35/18 up front and 295/35/18 out back......probably will go to a 305 or 315 out back once it's time

Rick@RKT Performance

I guess I'll be opening the 3.90 box. . Thanks to all who have contributed.

CuZ06

Looks like the decision has been made.....3.90s it is....

bumble-z

Good choice.
You wouldn't have noticed much of a seat of the pants difference with the 3:73's

You will be able to tell the difference with the 3:90's, especially if you have some new sticky tires in the rear.

Your car is in the Rick/right hands.