Has anyone changed there gears to 3.15 or 3.42 or something in the auto 6 speed cars?
Is this possible?

thanks,
Lusky

 

Biggest issue you are going to have is calibration. Right now, I don't think anyone can tune the A6 TCU.

Jersey

 

From what I understand you don't need to calibrate anything with a gear change in the Vette because it is read at the tire or something like that...can someone chime in

 

Anyone know how much it would cost to do this?

 

A 3.15 with a A6 will make low gear sound like a creeper gear.
GM has already compensated in the lower gears of the A6 for the taller rear end.

 

The 3.42's are to low for street use with the A6, 3.15's are what I want and would be as low as I would go in a A6 street car. Flooring the throttle from a stop will get you plenty of wheelspin with the 3.15's, so you will need a sticky tire, or you have to learn to feather the throttle on take off until the car is hooked up, then floor it. You know you have to pay the "Corvette tax" on everything you buy for this vehicle, I know its high for a gear change (paid 400 including gears in my Mustang), But with that said, I have heard the price of a gear change in a Vette is around $1000-1500. If anyone knows different, please chime in.

 

No, the speedo sensor is in the tranny. The wheel sensors are only for ABS and AH. So you need to recalibrate the speedo by editing the TCM, and you'll need to reprogram the shift points so they'll be appropriate for the new gearing. Since the TCM for the A6 is brand new (32 bit), it'll be a while before the aftermarket learns how to program it.

 

Is this a change from the C5? I thought the C6 was the same. C5s had the speedo sensor on the output side of the diff. No programming was needed to correct the speedo, though A4s needed programming to correct the shift points, and prevent a "tranny slippage P1870" code. See this link. A4 Differential change

As for ratios, maybe this a good use for all those 2.73 gears the 05 A4 guys have been getting rid of.

 

C6 manual ratios is the same for the C5, speedo pickup in the diff. Not sure about the location in the autos but it is not in the diff.

 

send it to lingenfelter they will set u up have the motor built while its there

 

I agree a 3.42 would be way to steep. I think most will opt for a 2.73 when the dust clears. I really have a feeling the 3.15 would be to low a gear in the A6. Good thing about that is the 2.73 rear will be a dime a dozen in a year or so.

 

Do you know if the gears in an 05 would work in a 06, I know for 06 they changed some parts in the rear?

 

I do not know. I am anxiously awaiting the first post of someone who has done the mod to get the real scoop.

 

 

Yes the gears will work.

 

I'm having a 3:15 installed in my 2011 c6 A6 auto tranny. I'm not concerned about the physical change, just the computer stuff. What all has to be changed and where?

really concerned
Jeff

 

This is an 11 year old thread you dug up from the dead, so much of the info is outdated.

Almost any tuner can change whatever needs done as far as the computer is concerned.
I should mention that a higher stall converter will work wonders without a gear change and at a lower cost.

 

A converter swap makes more sense, in terms of returns (ET-wise) at the track, than a gear change. But, the taller (lower numerically) stock gears will load the converter more and make the car feel "lazier" during low part throttle driving and starting off from a stop, until you get the car going fast enough that the TC clutch locks up.
There's plenty of more recent threads on this on here, with all of the back and forth debate about this.
The 3.42s are going to be a little steep for most folks with the A6, especially coming from a 2.56, but it doesn't make first gear "useless" like you will see most naysayers post on here. For a simple SOTP mod, there's nothing that "wakes the car up" better.
I installed a Z06 Diff (with 3.42 gears) in my A6 GS a couple of years ago, when it was still N/A, which I did along with a converter swap to an FTI 3600 at the same time. Those two things made the car feel like a completely different car.
I'm now seriously considering just putting the stock 2.73 rear back in it, because my car has no traction off the line now, even with 345 NT05Rs, since I installed a blower.
I have to say though, that I wouldn't want a 2.56 gear either. I think either a 2.93 or 3.15 is probably closer to being the optimum gear for the A6, from my own experience.
Question is, do you want to spend around 2 grand just to make your car feel a little bit better?? Ummm, I think a lot of us have already answered that one in the affirmative.

 

Old thread but relevant though lots of miss information above post by CI is rite on about A6 and diff gears if staying N/A 3.42 is it, I went from 2.73 to 3.42 and is just perfect always look for 12 to 13 to one 1st gear reduction for N/A performance is rite on specially combined with a nice stall converter.

Definitely must enter new diff ratio at engine files after changing diff gears to a different ratio.

A word of caution for A6 owners having tranie tuned, firming up gear shift 2nd to 3rd will cause the backing plate behind the clutch pack to "cone in" if over done and result is going to Rev limiter no gear change, so if you 2nd to 3rd changing fast and feithfull live it along cause the fix is expensive.

 

It's been well documented that the change from a 2.56 to a 3.42 is worth .10 seconds in the 1/4 mile.
Part of the difference is the 2.56 gear will be at peak RPM around the 125-130 MPH finish line in 3rd gear vs the 3.42 matches the RPM and MPH in 4th gear, but with one extra shift. The .10 is because the 3.42 gear allows the engine get to peak RPM quicker and exist in the higher power range for a longer time.
Neither the 2.73 or 3.15 gear will cross the stripe near peak power, since the shift to 4th puts the engine at the low end of the curve.