3:15 to 3:55 Gears - Anyone have a before and after quarter mile timeslip?

[MrJFK65]

I recently bought a 2016 California Special Convertible - Automatic. I purchased a Performance pack II (Cold Air Kit-Ford Tune-Throttle body) that I will take to a dealer to install so that I keep my factory extended warranty.

This is not a daily for me, but I will likely take it on long trips to the beach, mountains, etc.. I will also take it to Test n Tune day at Atco Raceway in NJ. I usually do that 2-3 times a year. I've pretty much done that with all of my cars. Always interesting to get a "time on the car" before I start modifying it.

I've searched the site before I posted this and found threads that discussed the merits of adding the steeper gear versus leaving stock, that included tech information on what RPM the car would be at 3:15 vs 3:55 amongst a lot of other very useful pieces of information. A lot of the information was observational/antidotal, and I'm a facts and figures kinda person.

How much did your E/T drop (Or heaven help me increase) for anyone that made this switch on an Automatic?

In the end, I'm trying to get as low of an ET as possible naturally aspirated on street tires. I'd be very happy with anything under a 12:40

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[2016S550]

I read many threads on the two ratios and if I recall correctly the 1/4 mile with the 3:15 gear actually had a better ET. Cannot comment on the 60’ time. Seat of the pants feel went to the 3:55

 

[MrJFK65]

I’m actually pretty surprised that no one has tested this theory?

Doesn’t Ford use the 3:55’s in there PP?

 

[LSchicago]

I read many threads on the two ratios and if I recall correctly the 1/4 mile with the 3:15 gear actually had a better ET. Cannot comment on the 60’ time. Seat of the pants feel went to the 3:55

I don't believe that is true on a stock car. My car with 3.55's ran 11.92/118 bone stock with 340# driver. 1.87 60' times on P Zeros. Not a PP car either.

 

[Chef jpd]

If you are going to swap gears, a 3.73 or a 4.09 might be a better option.
Both can be adjusted with the Ford Calibration software you get with the performance pack.

 

[mtr5.0]

I am really interested in this too. really surprised Havnt seen any dragstrip test 1/4 mile. Both cars in stock form…

 

[LSchicago]

I am really interested in this too. really surprised Havnt seen any dragstrip test 1/4 mile. Both cars in stock form…

I test drove both back to back when I bought my 2018, and the 3.55 was definitely quicker, so that's what I bought.

 

[2016S550]

I don't believe that is true on a stock car. My car with 3.55's ran 11.92/118 bone stock with 340# driver. 1.87 60' times on P Zeros. Not a PP car either.

I misspoke, about a tenth in the 1/4
60’ diff was .07 which makes no sense since everyone comments on how much faster the 3:55 gears are from a stop. Post 39

No connection, just something I saw while Researching the same question. I was about to buy a 3:15 car but wanted 3:55. The consensus I came to was that the 3:55 consistently felt quicker on the butt dyno. Nobody who bought 3:55 regretted the decision. And 3:15 was preferred by those Boosted owners.

https://www.mustang6g.com/forums/threads/a10-3-15-vs-3-55.102804/page-2

 

[CUL8R]

As mentioned by Chef jpd, you should consider the jump to 3.73's or 4.09's. You'd notice the difference then for sure. My 20 came with factory 3.73's and they're an all round great choice for city or highway, and launch well. Enjoy whichever you choose!

 

[LSchicago]

I misspoke, about a tenth in the 1/4
60’ diff was .07 which makes no sense since everyone comments on how much faster the 3:55 gears are from a stop. Post 39

No connection, just something I saw while Researching the same question. I was about to buy a 3:15 car but wanted 3:55. The consensus I came to was that the 3:55 consistently felt quicker on the butt dyno. Nobody who bought 3:55 regretted the decision. And 3:15 was preferred by those Boosted owners.

https://www.mustang6g.com/forums/threads/a10-3-15-vs-3-55.102804/page-2

I decided to keep the 3.55's with boost. They work well with the A10/Procharger P1X. I just went with 29.5" tires to hook better and reduce the effective gear ratio close to a 3.31. Keeps the car in 6th at the strip too.

 

[mtr5.0]

I have the 3.15 gears, I’m going to go with the 26” tall M/T et street R (275/40/17 ). Should help me out of the hole somewhat. Was thinking of swapping out the 3.15 for a 3.55. But down the road I plan on doing a whipple blower…

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