Gear swap?

[04lss]

Hi All,

I am looking to improve the acceleration and pull in my 2019 mustang GT MT. I am considering swapping the rear end gears for something shroter from ford perf. Right now it has the 3.55 gears and they feel too tall for the torque the engine has down low.

I have a few questions for folks.

1. If you had yours installed by a shop, how much did you pay?

2. What ratio should i go with? Ideally id like to be at 2500 RPM or less at 70 MPH. Currently im at about 2k.

3. Will it make a big difference? The car is fast enough. I know that from having it on a track and having a c7 corvette just barely pull away. It just doesn't shove me back in my seat the way i want. Tuned GTI with the Golf R turbo throws me back in my seat and thats what id love to get out of my GT.

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[Schwerin]

I'd just get 4.09 and be done with it. The MPG difference on the highway would be maybe 1-2. I had same final gear and a 4.10 in my 2003 mach1 and I used to go to clients from up to NYC to NJ, Philly and down to DC. The bigger issue was the loud exhaust I went with than the gearing.

 

[Stang 19]

Wellllll, lt’s not exactly what you want to hear, but ...it you want a serious shove, leave the bears as is, install a supercharger. Get either an Edelbrock or Whipple complete kit with tuner. These are both well engineered kits.

 

[ice445]

Yeah, you're not gonna get huge gainz from taller gears. Unless all you do is stoplight race, the 3.55 is kinda nice because you can really wring out 3rd without having to shift. If you're gonna swap gears, I'd just swap the pumpkin for a torsen one while you're at it. The stock differential is still a perfectly functional limited slip, but it uses clutches instead and they wear out eventually.

I suppose it's worth considering as well that 18+ has taller gears in the transmission itself, so if you went to a 4.09 you would probably be equal in gas mileage to an older car with 3.73's, or at least close enough to justify it.

 

[cib24]

The 2018+ gearing truly kills the car. The 15-17 is quicker for sure up to about 100 mph due to much better gearing despite being down on power. I have a 4.09 and a Torsen ready to fit but will need to wait for the lockdown to end to have them installed. I can't wait because:

1. Drag racing the 3.55 and the revised manual transmission ratios on the 2018+ means you have terrible off the line performance;

2. When you shift you drop down too far in RPMs in the next gear;

3. When hustling on a back road the 3.55 and long gear ratios means you never leave 2nd gear and barely use 3rd, and I'd prefer more interaction below 100mph.

See a comparison of the gearing:

 

[ice445]

The 2018+ hearing truly kills the car. The 15-17 is quicker for sure up to about 100 mph due to much better gearing despite being down on power. I have a 4.09 and a Torsen ready to fit but will need to wait for the lockdown to end to have them installed. I can't wait because:

1. Drag racing the 3.55 and the revised manual transmission ratios on the 2018+ means you have terrible off the line performance;

2. When you shift you drop down to far in RPMs in the next gear;

3. When hustling on a back road the 3.55 and long gear ratios means you never leave 2nd gear and barely use 3rd, and I'd prefer more interaction below 100mph.

See a comparison of the gearing:

The car definitely looks like it would be more fun with 4.09's, looks like the perfect setup for the newer cars. How much did your goodies cost you out of curiosity?

 

[cib24]

For me it cost about £1,400 ($1,600-1,700) to get the torsen, 4.09 and ring and pinion install kit. However, I had to order them in the US and ship them over to the UK and pay customs charges so I got a little bit raped compared to someone just buying and fitting the parts in the States.

Just the gears and install kit would have been about £450-500. The torsen was pricey but I do track days so it's more valuable to me than the default LSD which itself would be fine for drag racing.

I have been quoted £400-500 to remove the pumpkin, install everything and reinstall the pumpkin.

 

[ice445]

For me it cost about £1,400 ($1,600-1,700) to get the torsen, 4.09 and ring and pinion install kit. However, I had to order them in the US and ship them over to the UK and pay customs charges so I got a little but raped compared to someone just buying and fitting the parts in the States.

Just the gears and install kit would have been about £450-500. The torsen was pricey but I do track days so it's more valuable to me than the default LSD which itself would be fine for drag racing.

I have been quoted £400-500 to remove the pumpkin, install everything and reinstall the pumpkin.

Yeah, after some digging it looks like the full upgrade cost for everything is just a touch over $1000 in the US, maybe a little less if I can find some deals somewhere. So not terrible, but the labor is killer. I can do a lot of stuff on my own, but setting the correct lash and all that with a new gear set is not in my skill set, lol. Regardless it will probably be the first upgrade I go for since I like shifting.

 

[cib24]

I bet it's the best bang for the buck seat of the pants mod except for swapping in the old MT-82

 

[Ebm]

The price depends on your area and whether you want to replace anything while re-gearing. Ring and Pinion kit will run you between $150 and $300 depending on where you get it from. Labor from a reputable shop around here runs $800 or so and usually includes gear oil and a few other things. That $1000 estimate is accurate.

Nothing wrong with attempting a re-gear if you're pretty mechanically inclined. Plan a whole day and make sure you have ALL tools ahead of time. Measure twice, cut once still applies here. Double check your work before moving on to the next step. The consequence of messing up is a little higher than most jobs. Ranges from gear whine to completely blowing the thing up on the highway.

4.10s are fun, but if I had to do it over again, I would lean towards 3.73s over 4.10s. Acceleration makes up for the lack of grunt down low and you have a more balanced car in my opinion. 1st gear will be a relic as you'll only use it when launching(drag strip) or on a steep hill. I usually start off in 2nd but the car is capable of starting off in 1st, 2nd, or 3rd gear without bog. In the city, I usually go 2nd, 4th, 5th, 6th. You make up a little bit of mileage in the city because it's easier for the car to accelerate, but lose that mileage on the highway and it all becomes a wash. I'm averaging 19-20 mpg with 4.10s. If you go with a bigger tire than stock, it effectively reduces the gear ratio and you hit a sweet spot this way. 275s and 3.73s or 295 or 305s with 4.10s are great combos.

 

[cib24]

I don't see how the 3.73 is a better option if you have a 2018+ Mustang. 4th, 5th and 6th are basically different shades of overdrive gears when you look at the speed chart in my previous post. So, for around town driving I wouldn't expect any drawbacks as you have 6 gears to play with, and on the motorway you likely won't see any real decrease in mpg given the RPM gain is so modest, like 300-400 RPM.

1st gear in a 2018+ with 4.09 will be almost exactly the same as a PP1 2015-17 Mustang GT with the 3.73, so it's still a usable gear.

I say don't fear the gear, and if it was possible, I would have tried 4.3 or maybe even 4.56.

 

[cib24]

Another chart showing a 2018+ Mustang highway cruising mph. Gear changes in this one are at 7400.

 

[AZ18yote]

Have you considered tuning for e? Makes these cars a completely different animal.

 

[cib24]

Yeah, for certain States you are lucky to have that option. Over here in the UK, the best we get is your equivalent of 94 octane and UK cars have a cat and GPF so Lund, Steeda, Ford Performance and other tunes from US tuners are not compatible. We can delete those items and then tune the car but then we cannot pass emissions.

In either case, I still think gearing should be the first mod on a manual 2018+ GT as it will make the most difference to driver enjoyment.

 

[Mikepol2]

I went from 3.73's to 4.09's at a total cost of $611 ($225 labor and the rest parts / tools / fluids) and at that price it was very worthwhile, but I removed and reinstalled the differential myself. It created additional force to the road from the rear wheels equivalent to if I had increased the engine torque by 40 ft-lbs. Normal dealer cost is around $1200 plus parts, 2/3 of the dealer labor time is removing and reinstalling the diff. In my mind the most important thing you can do is find someone you trust to install the ring and pinion into the housing.

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