2017 Mustang gear ratio change?

[Coyotes55086]

Hey guys, so I have a 2017 Mustang. I'm still unsure on how to find what gear ratio I have. But I've been watching a lot of videos saying that changing to 4.10 gear ratio is going to make the car accelerate much harder. Is this true and what do you guys think about this?

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[subbz]

If you have the performance pack then you should have the 3.73. Changing the gear ratio to 4.10 would definitely make it accelerate harder but might also be overkill for the s550. Get a tune and change the throttle response first cause the way the drive by wire is set up it makes the car very sluggish. Even using a throttle response controller can make a big difference.

 

[Coyotes55086]

Mine is just gt premium with no performance package . And thanks for the input man .

 

[Shifting_Gears]

It would make a drastic difference on your car.

Are you manual or auto?

Other part to consider is your driving style. A higher gear ratio will increase RPM at cruising speed so if you do a lot of highway driving, that’s something to consider. Not an issue other than the effect on gas mileage.

If you do the swap you will need to have the speedometer calibrated for the new ratio. Most people do this through a tune.

 

[ugstang17]

There is an axle code on the vehicle GVW sticker located in teh drivers side door jam. That code will determine what gear is in the car if it has never been swapped out.

A simple way to determine axle ratio is to jack the rear end up, put the car in neutral. Place a mark on the inside of the rear wheel and another on the driveshaft. Begin turning the driveshaft by hand counting the total rotations while observing the tire as it completes one full rotation. E.G. Slightly more than 3.5 rots of the DS to 1 rot of the rear tire equals a 3.55 gear. Crude but effective method. The only time this may not be precision enough is when determining between a 3.15 and 3.31 gear.

 

[Coyotes55086]

My car is an auto 2017 gt . Most of my driving is in the city . In the future I am planning on adding some FI but this may not be for another year

 

[Ebm]

Changing the rear-end gears will make it accelerate faster but the trade offs are your car will shift gears more often and have a lower top speed. This change will provide fun at a lower speed as well as give the car life at a lower rpm but still do illegal things at higher speeds.

I don't have an auto, but I have the MT-82(manual) with 4.10s out back. I can start off in 1st, 2nd, or 3rd gear without bogging. She gets wild too. Spins a little higher on the highway but you have a little more oomph around the city. If you decide to go through with it, for the love of all that is good, find someone that is a professional and does gear changes often. Otherwise, there's a good chance you'll end up with noises, especially on deceleration.

 

[ugstang17]

As for advice on what gear it depends on what FI setup design you go with and what you plan to do with the car. People can give open opinion without 411 to base on all day long based on their use of car, however to get the best feedback I suggest discussing what FI setup you plan to go with, and what you pan to use the car for. Additionally what plans are being made if any to stall the trans via a converter. That also weighs in on gearing. Is a transbrake in the plans as 15-17 models don't come with that track option. A car being setup to run 1/8th mile on FI won't be geared the same as a car being set up for 1/4 mile, just as a course car won't be likely geared the same way as a strip car. How much street use will the car see or will it be a trailer queen that only sees the track? What tires are you planning to run? There was a time when all I thought a person had to do was shorten the gear and poof! But its not that simple if you want to optimize the setup for your application.

 

[Coyotes55086]

So I think I'm leaning more towards a twin turbo kit at the moment. This car is going to be a daily driver. Lol . I know it's crazy but I want it to be mean when I need it to be. Most pulls are going to be odd highway pulls and empty road pulls . As far as tires I've been seeing a lot of good things about Toyo r888r ?

 

[Cobra Jet]

Unless I missed it - look under the rear of the car. On the back of the diff pumpkin cover, there should be a white decal attached to the cover. The gear ratio is listed on that decal.

Of course if someone messed with the rear differential by swapping the whole diff OR just the gears, you’ll have to use other methods of determining as noted above.

Here’s a pic from my 2018, the code on the tag of “3L55” is a 3.55 rear. It’s also a Torsen rear.

TIP:
- If the rear diff has Trac-loc guts, you won't be able to see through it with axles removed. There will be a "bar" in the hole which is for the spider gears.

- If the rear diff has Torsen guts, you'll be able to see through it with axles removed.

 

[LxMike]

The coyote mustangs seem to like a 3.15 or 3.31 gear especially with a power adder. If your going power adder try what you have first and see how the car feels.

 

[Zrussian13]

4.10 is good for na car but your going to limit the amount of time your car makes boost once you go twins. Especially if you go big twins like it sounds like you want too.

 

[ugstang17]

So I think I'm leaning more towards a twin turbo kit at the moment. This car is going to be a daily driver. Lol . I know it's crazy but I want it to be mean when I need it to be. Most pulls are going to be odd highway pulls and empty road pulls . As far as tires I've been seeing a lot of good things about Toyo r888r ?

So you are looking more toward rolling into pulls going WOT from a roll of 50-60. Also I am assuming you will be keeping the transmission stock with regard to a stall converter and/or transbrake. A 3.31 or 315 would be the happy choices IMHO. I put down 631RWHP through a PD setup. The car has a 3.15 gear with a stock trans. With a 28.6" tall Nitto 555 Extreme DR on the rear, at WOT commanded throttle in DRIVE the car will downshift into second at 50MPH bobble just a bit, break traction for a split second and then go on a warm sunny day. On cooler days if I feel the need to make a pull for fun out on an open stretch with no one around I will lock it in 3rd and shift it into Drive at about 6000.

A turbo setup -- as I have mentioned before in other threads -- with a boost controller is an awesome thing to have from what I have read on those setups. I was looking into pulling my PD setup and going that route, but it's more money than I wish to spend at this point. I'd be as happy to trade for a 13/14 GT500 or even a 12-15 ZL1 with a stick and man pedal and make some minor mods than to do a turbo swap on the current car with an auto in it. I have about lost the enthusiasm for going to the track on a TT night to mike passes, so the auto -- other than easier to drive in heavy traffic -- is becoming quickly boring. I miss seeing a white ball shifter in the car.

Good luck. BTW - OP! Love the shot of the Mustang going through the snow in your avatar. I drone previous Mustangs in all weather -- even snow -- to/from work.

 

[Coyotes55086]

So you are looking more toward rolling into pulls going WOT from a roll of 50-60. Also I am assuming you will be keeping the transmission stock with regard to a stall converter and/or transbrake. A 3.31 or 315 would be the happy choices IMHO. I put down 631RWHP through a PD setup. The car has a 3.15 gear with a stock trans. With a 28.6" tall Nitto 555 Extreme DR on the rear, at WOT commanded throttle in DRIVE the car will downshift into second at 50MPH bobble just a bit, break traction for a split second and then go on a warm sunny day. On cooler days if I feel the need to make a pull for fun out on an open stretch with no one around I will lock it in 3rd and shift it into Drive at about 6000.

A turbo setup -- as I have mentioned before in other threads -- with a boost controller is an awesome thing to have from what I have read on those setups. I was looking into pulling my PD setup and going that route, but it's more money than I wish to spend at this point. I'd be as happy to trade for a 13/14 GT500 or even a 12-15 ZL1 with a stick and man pedal and make some minor mods than to do a turbo swap on the current car with an auto in it. I have about lost the enthusiasm for going to the track on a TT night to mike passes, so the auto -- other than easier to drive in heavy traffic -- is becoming quickly boring. I miss seeing a white ball shifter in the car.

Good luck. BTW - OP! Love the shot of the Mustang going through the snow in your avatar. I drone previous Mustangs in all weather -- even snow -- to/from work.

Thanks for your help and responses brother !

 

[Coyotes55086]

I found out today I have 3.73 on my Mustang already. Will switching to a 4.10 gear ratio be of a difference? Or would the switch not be worth it?

Or even going higher?

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