First Mustang 2016 GT Premium - a question

[andreop]

Deep Blue Metallic GT Premium purchased a few weeks ago Certified pre-Owned. One of the options it has is a 3.55 Ratio limited slip rear axle. What does this mean as far as performance is concerned? For example, is there more torque and horsepower at lower speeds?

The car also has 20" wheels, spoiler and auto trans. This is my first mustang. The car is great and I look forward to posting some impressions after I log 1k miles or so

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[The Icemans 5.0]

Deep Blue Metallic GT Premium purchased a few weeks ago Certified pre-Owned. One of the options it has is a 3.55 Ratio limited slip rear axle. What does this mean as far as performance is concerned? For example, is there more torque and horsepower at lower speeds?

The car also has 20" wheels, spoiler and auto trans. This is my first mustang. The car is great and I look forward to posting some impressions after I log 1k miles or so

Deep Impact Blue. 3.55s are great. You got a good car.

 

[Rick#7]

Welcome to the world of insanity known as Mustang ownership LOL

3.55 gears don't change the engines hp or torque output, but it does increase torque at the rear wheels compared to the standard 3.15 gears because of the increased torque multiplication. It's a simple mechanical principal, but what it means in the real world is your car should accelerate quicker than a 3.15 geared GT, all else being equal.

If you intend to race the car, it also means you'll hit the Rev limiter at a lower speed, but that's not usually an issue on the street.

 

[andreop]

Welcome to the world of insanity known as Mustang ownership LOL

3.55 gears don't change the engines hp or torque output, but it does increase torque at the rear wheels compared to the standard 3.15 gears because of the increased torque multiplication. It's a simple mechanical principal, but what it means in the real world is your car should accelerate quicker than a 3.15 geared GT, all else being equal.

If you intend to race the car, it also means you'll hit the Rev limiter at a lower speed, but that's not usually an issue on the street.

Thanks Rick#7. This explains it well. I am glad the car came with it.

 

[jefffrot]

On the down side, the 3.55’s may negatively effect your MPG’s slightly because you will be running at a higher rpm at cruising speed. It all depends what is a important to you. A little more low end grunt or a little better economy.

 

[andreop]

On the down side, the 3.55’s may negatively effect your MPG’s slightly because you will be running at a higher rpm at cruising speed. It all depends what is a important to you. A little more low end grunt or a little better economy.

Thanks for the response. I have noticed the highway mileage is different from EPA estimates. It's probably from the 3.55 rear as you say.

 

[17Magnetic5.0]

I also have the 3.55 automatic. Basically our cars will get off the line faster assuming you can get traction though I've never had an issue with traction other than wheel hop. The cons as mentioned before are that mpg will be lower and top speed will also be lower. Also if doing quarter mile racing it might require an extra shift. Also I believe the diff housings are different as I know some people can't go from 3.15 to 3.55 without a whole housing swap. Also since you're new to this I might mention that if you have the 20 inch factory wheels your car more than likely has a slightly better suspension as it would have the k brace connecting from tower to tower as well as the lower k brace underneath the car.

 

[Rick#7]

.... Also I believe the diff housings are different as I know some people can't go from 3.15 to 3.55 without a whole housing swap.

This might be a little off topic from the OP's question, but this is partly correct. The housing is the same regardless of the ratio, it only varies from aluminum for auto trans cars to iron for stick shift cars. The differential itself inside the housing is what needs to be matched to the gears.

Ratios of 3.15 and numerically lower require a different differential than 3.35 and higher ratios. Because of the expertise and specific tools required to properly set up new gears it's often easier and cheaper just to swap loaded differential housings than to install new gears. Maybe that's where the confusion comes from with people thinking the housing needs to be changed, but it's not a requirement, it's just easier.

 

[andreop]

I also have the 3.55 automatic. Basically our cars will get off the line faster assuming you can get traction though I've never had an issue with traction other than wheel hop. The cons as mentioned before are that mpg will be lower and top speed will also be lower. Also if doing quarter mile racing it might require an extra shift. Also I believe the diff housings are different as I know some people can't go from 3.15 to 3.55 without a whole housing swap. Also since you're new to this I might mention that if you have the 20 inch factory wheels your car more than likely has a slightly better suspension as it would have the k brace connecting from tower to tower as well as the lower k brace underneath the car.

Thanks for the response. It does seem to handle well, perhaps that is due to the k brace you mentioned. I am still getting used to the acceleration. I will primarily be driving on country roads, so I will be following all posts regarding suspension/handling issues. So far the car is a blast.

 

[17Magnetic5.0]

This might be a little off topic from the OP's question, but this is partly correct. The housing is the same regardless of the ratio, it only varies from aluminum for auto trans cars to iron for stick shift cars. The differential itself inside the housing is what needs to be matched to the gears.

Ratios of 3.15 and numerically lower require a different differential than 3.35 and higher ratios. Because of the expertise and specific tools required to properly set up new gears it's often easier and cheaper just to swap loaded differential housings than to install new gears. Maybe that's where the confusion comes from with people thinking the housing needs to be changed, but it's not a requirement, it's just easier.

Ah ok yeah most of what I had seen on YouTube was people just swapping out the whole thing so I figured it was required. I also just wanted to let OP know about some of the other things his car has

 

[17Magnetic5.0]

Thanks for the response. It does seem to handle well, perhaps that is due to the k brace you mentioned. I am still getting used to the acceleration. I will primarily be driving on country roads, so I will be following all posts regarding suspension/handling issues. So far the car is a blast.

Yeah I think me and you are basically in the same boat here I also got a 17 premium also CPO but I got mine a while back. I too do country road driving and have a lot of twisty roads, the only thing I have done to mine is add the factory k brace and the strut tower brace but since I'm assuming you already have the k brace then the strut tower brace is a good place to start when you start modding.

 

[GT-SV]

Andreap - Sounds similar to my 2016 GT Premium w/20's except mine has 3:15 rear end. My gas mileage is within 1-2 mpg of EPA highway rating with typical cruising speeds 75-80 mph. Enjoy your new GT!

 

[andreop]

Yeah I think me and you are basically in the same boat here I also got a 17 premium also CPO but I got mine a while back. I too do country road driving and have a lot of twisty roads, the only thing I have done to mine is add the factory k brace and the strut tower brace but since I'm assuming you already have the k brace then the strut tower brace is a good place to start when you start modding.

What does the strut tower brace do?

 

[andreop]

Andreap - Sounds similar to my 2016 GT Premium w/20's except mine has 3:15 rear end. My gas mileage is within 1-2 mpg of EPA highway rating with typical cruising speeds 75-80 mph. Enjoy your new GT!

Thanks, you too. My highway mileage is down about 3-5mpg from EPA ratings

 

[Shifting_Gears]

What does the strut tower brace do?

Bridges the two strut towers together to lessen chassis flex.

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