I have a '14 GT 5.0 with a Whipple/Ford Performance Supercharger, 3.00 inch pulley, Stainless Works long tubes, off road H pipe, and a Borla Touring exhaust. It's on E85 with the stock rear end and an auto trans. I'm thinking about doing a rear end upgrade with Moser axles and the Ford Racing 4.10 gear kit. What can I hope for in the 1/4 mile? The car dyno'd at 626/530 before the gear swap. Are 4.10's the best gears for the 1/4 mile?

 

Gearing depends on the use of the vehicle. For a daily driver, you don't want to go more
than +10% on the gear ratio. 4.10 is probably ideal for your setup as a daily, but if you
want DRAG, you can go higher.

So, you have a 3.73, 10% higher is 4.103. That would be your calculated ideal daily
driver gearing, so you would go the closest to that you could, which is 4.10. I had a
Charger with 2.87, calculated to 3.10, but the closest was a 3.19 carrier, which was available.
However, scrolling eBay; for $50.00 I ended up going 3.64. Lost about 3 MPG on the highway,
and it got worse as higher speeds were reached. Was a simple carrier swap 2 hours, and boom...
RPMs were 300 higher final gear. SO, at 70MPH it was 2800 RPM, went up to 3100, something
like that. That was the NAG1 5-speed auto. 1st gear was like it didn't even exist, it went
through it so quickly... Still had to buy the tuner to change the gear ratio in the TCM.
The NAG1 has a seperate TCM, which basically acts like a translator for the NAG1,
which is a mercedes transmission. Dodge tranny diidn't have the separate TCM, the
ECU handled it all.

 

Do you have an automatic or manual? Gear selection is more than just "what do I put in the rear end" type of question. The transmission ratios need to be considered as well. And for an automatic, a 4.10 will cause you to shift quickly from 1-2, probably before the 60' at the drag strip. It isn't ideal for an automatic, and as I recall it isn't considered ideal for a manual either

 

A tune can change the shift RPMs, but no matter what, it will shift if it hits
the rev limiter (automatic).

 

Unless you have upgraded your rear gear already, auto's come with something in the 3.30's range stock and 3.50's range optional. I wouldn't go more than 3.73 in either case. That much horsepower just doesn't need it.

 

3.31s or 3.55s. Also depends on your tire selection. I’d do 3.55 with a 28” tire.

 

For a daily driver, you take your ratio "x.xx" and divide by TEN, then add your gear
ratio "x.xx" to that result, for your new ratio.

If YOU want more, it's up to YOU, not everyone else.

You didn't specify manual or automatic, they come with different ratios OEM:
Code / Ratio / Type / +10%
GG / 3.31:1 / LS, Opt V6, GT Man, GT500 / 3.64
GG / 3.31:1 / Torsen GT500 SVT Perf / 3.64
DD / 3.55:1 / LS, Opt GT Man / 3.90
BB / 3.73:1LS, Opt GT Man / 4.10

If there is no 3.64 option from 3.31, you'd round to 3.55. No 3.90 option, so you go to 3.73,
and so on, unless you can get the ring and pinion combination. Using factory ratios, is
where you round to the nearest one to 10%. The LX platform dodge/Chrysler has so many
rear carrier options, I had many to choose from. However, replacing the differential on the
LX is easy, the unit itself comes right out, and goes right in. Then, you could even use the
larger ones and use larger axles. They had three different sizes, with a multitude of gear
ratios. I mean, you literally remove three bolts, pop the axles out, and all you have is a DIFF
in your hands. Putting the replacement in, reverse of removal. I takes 2 hours, less if you've
done it enough times. Changing the axles is what takes longer, like going from 198RII to a 210RII
or 215RII, you got some more work ahead... RII is the DIFF, they call it a rear independent iron...
SO, yeah, I went from 2.87 to 3.64, my other options were 3.07 and 3.90, but man, $50.00
for the 3.64, I jumped on that...

 

4.10S with an 6r80 auto is a mistake

3.15s have shown to be fastest for the 1/4

 

Depends on setup. Too vague to say that 3.15s are the fastest.