NosLaser

I am asking this specific to the Z06 trans group as my searches seem to have people chiming in with A4 cars, and non-Z06 6MT's that will likely see different results.

The car is not a daily driver, however it is certainly not a track car. I am considering either 3.73's, 3.90's, or 4.10's.

I'm leaning towards the 3.90's as a compromise between too much, and the jump from 3.42's to 3.73's possibly being not enough.

The car as of now is simply a CAI/X pipe combo, but I also has a Nitrous Outlet 100 shot, and plans are for a custom FTI cam/springs pkg, an ATI dampner, and long tubes/X combo.

I'd like to stay in 4th gear through the traps (which with a good tune should be in the lower 120's; maybe 122-124ish) on motor, with a shift into 5th if necessary on bottle.

What are some forum member experiences with rear gear swaps from both a driveability and performance standpoint, and if you had to do it differently would you?

NVNO1

A really good friend of mine did heads/cam, fast, tb, headers x pipe, air intake. Can't remember what it made on the Dano, but he said he was really disappointed with the car. He said it really didn't feel that much stronger after all the upgrades. After all that he then added 410s. He said it was a night and difference once the 410s were installed. With the power upgrades and 410s he said the car was an absolute beast. To time slips however. All seat of the pants. I'd be curious to know how a stock c5z would respond to 410s only.

Dennis Wilson

IMO 3.90`s are perfect. Redline in 4th. is around 130+ I have my limiter set to 6800 which makes it around 136. Drivability is great, have been on many road trips incl Bowling green . Mileage will drop a bit, but who cares? RPM at 80 will be around 2250 in 6th. Do it! you won`t regret it!

dork

Funny, I just posted about my mods for performance in another thread less than 2 minutes ago... lemme cut and paste: I'm not quite sure if you already have a bottle or if that's part of your plans. You say, "The car is not a daily driver, however it is certainly not a track car.", which gives me the impression that you wanna 'compromise' between the two for both. If that's the case, I would choose either the 4.10's (only) vs. H/C/I as a dichotomous path... one or the other, but for streetable applications, not both, especially on the bottle.

I have no experience here--this is just my WAG, but gears, H/C/I, and a bottle will require both a clutch upgrade and tranny/differential braces. (Everything I remember having read leaves me the impression that your 3-'methods' combination will put tremendous strain on the drivetrain.)

I'd advise that you do some heavy research (reading) on H/C/I combinations in consideration of your final goals for this car, and then talk to 2-3 speed shops to see what they recommend. But...

I've read this complaint about H/C/I combinations several times before; it's why I was leery about speed shops' preferred recommendations vs. my wants; and from previous gear-swap experience in other cars, I knew lower gears would be an absolutely satisfying mod (if not one to finish with). Momo heads, which springs? cam? and what intake?--I was holding off, waiting for Atomic to get the z06 configuration correct when my clutch went out, and at that point I was forced into a financial decision...

I'm content with 4.10's as I wrote. I can't envision the car as a DD with the addition of H/C/I, but NO might be palatable since that isn't always 'on'.

75mph with 4.10's will hover at ~2300rpm; gas dropped from a hand-calculated 27.4mpg to 22.0-24.4mpg... everyone said I'd loose "1-2mpg" (NO ONE said I'd lose "3mpg"), but I can't keep my foot out of it, so I've not seen 25.4 yet. and don't care, neither

I forgot--I think you're right about 3.73's--'everyone says' 3.42 to 3.73 isn't enough.

danziger

Traction is going to become a serious problem with street tires...

C5Dobie

I was curious about this as well...having driven trucks w/ 4.10 swaps w/ the 6L80 tranny (I know not apples to apples since an auto but still 6 gears) and the SOTP feel in a 3 ton truck is significant, in a 3000 lb Z06? Yeah....I'd say "traction will be an issue" is an understatement. I suppose a new set of tires would have to be in the conversation as well.

3.90s would probably be the route I'd go myself

NosLaser

Thanks for all the replies. I'm thinking 3.90's are going to be the way to go. The car is always on Nitto drag radials, so traction shouldn't be TOO terrible, although it would require a bit more finesse I'd say with a gear swap.

The car already has a bottle on it, and has been sprayed like twice just to ensure the system is working properly, but I don't plan on spraying the car again until I can schedule a proper dyno tune (better safe than sorry.)

I think I'm more interested in this car being fun/quick on motor versus all out speed demon, as my other car is a 1200hp (soon to be more) twin turbo Cobra, so it handles those duties. A well thought out cam/headers/x/cai combo should produce ~430rwhp on motor with a good tune, and 3.90 gears will give me back some low end I may sacrifice with a mildly aggressive cam, with the spray for 2nd gear on at the occasional track visit.

Edit: Now the question is do I purchase a whole diff with 3.90's already installed? If I were to have them installed, should I purchase an install kit, etc or are the things like motive gear a direct swap?

dork

I researched 3 speed shops. Two of the three speed shops said they'd tried sub-letting out ring-and-pinion swaps before with bad results and eventually (joined the other and) decided just to advise their customers that they'd only swap entire differentials including a core exchange. They all said the tools were too expensive and the process too complicated to validate the cost vs. liability of getting it wrong.

Rookieracer

I have 3.90s in my 2002 daily driver and really like them.

JIMS SVT

I was curious about a Z06 trans and hearing. I've read that a Z06 trans and a 342 gear is like a m6 and 390 gear. So if you do a 410 in a m12 car would the first 4 gears be like a 488 gear?

0Chuck CoW

We always build 4.10s for them... Even with Z51. A small bump in the rev limiter and you're

crossing the line in 4th still.

I wouldn't do anything less.
Chuck CoW

c5z06owner

hey im in long island and im thinking og upgrading to 3. gears in my 04 Z06. car currently has tick performance sns stage 3 cam w an intake, 1 3/4 LT and off road x pipe w a borla stinger catback, car is a strick daily driver w 40 miles driven daily. i live in long island and my commute involves almost no highway driving , how will this affect mpgs? my gas comsumption is pretty bad as it is idk why

Scotty2000SS

So you're looking at $1000 to swap to gears??

c5z06owner

im interested on the 3.7 gears but would like to know how it will affect drivebility with the given details above