2011 5.0 A6 with stock 3.15s. Shifting into 4th in the 1/4 mile?

[Bmr4life]

I've been looking around and it looks like I'm the only person shifting into 4th with the stock 3.15 gears. My tires are MT DR. 275/40/17 which should be 26" diameter. I'm trapping 112mph.

Here's a vid I took where you can hear the car shift into 4th not far from crossing the finish line.

2011 Mustang GT/CS A6 at Atlanta Dragway. 12.793 @ 111.60mph - DA 2994ft - YouTube

My tune is from Steeda and accounts for my Offroad H and JLT CAI. That's it for engine mods. I checked the tune, Redline in Drive was set to 7k rpm. Yet my Dyno run which was in 3rd went to 7200rpm.

 

[calgarybandit]

I run 3.31 with 27.44 tire and I am shifting at 7500 RPM through the traps into 4th. Just change your tire size and you will stay in 3rd

 

[Bmr4life]

I run 3.31 with 27.44 tire and I am shifting at 7500 RPM through the traps into 4th. Just change your tire size and you will stay in 3rd

Crap, I didn't think about that. My tune is set for my 285/30/20's and not my DRs. So when I race, I should change the REVS/MILE and make the number higher.

 

[Bmr4life]

Arlight, I checked my tune out. I have the tire REV/MILE set to 785 which should be very close to my 26" race tires. So that's not the problem. I did find that my car is shifting at 6800rpm for the 2-3 and 3-4 shifts. That explains why I'm not staying in 3rd over the stripe. Problem now is figuring out why. Steeda is supposed to be getting back to me about the tune.

 

[Big Ben]

I have the exact same issue. I have been running 275/40-17 DR's also and am a 3.15 Auto trapping the same (NA). When I run on my 19" street tires I'm going through in 3rd no prob but run .1-.2 slower due to traction. I believe it's gearing difference of the smaller tires.

I am about to buy a new set of DR's and want to stay on my 17's for drag. Any recommendations on size. Was thinking of going some taller 17 inch slicks but really want to be able to drive to track and back on my setup.