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Ford 3.31 Rear End Gear & Install Kit | 15-22 - Mustang by Ford

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Details   |   Reviews
Ford 3.31 Rear End Gear & Install Kit | 15-22 - Mustang

Upgrade your 2015-2022 Mustang's stock rear end gears with a set of 3.31 gears from Ford!

Item #LRS-4209FRN-K

Everyday Low Price: $474.99

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  • Replaces Stock Gears
  • Improves Acceleration
  • Complete Installation Kit


  • 3.31 Gear Ratio
  • Steel Ring & Pinion
  • Bearings & Shims

 What's in the Box

  • See Below

2015-2022 Ford 3.31 Gear Kit

Improve your S550 Mustang's acceleration and throttle response with a set of Ford 3.31 gears. Featuring heavy-duty steel ring and pinion gears, upgraded bearings and shims, and all of the necessary installation components, this gear kit includes everything needed to complete the job. While these Ford gears do not increase horsepower, they will definitely allow your Mustang to launch harder and quicker!

Motorcraft Friction Modifier

This friction modifier is a specially formulated additive to provide smooth operation of clutch-type limited-slip differentials. 1 bottle of friction modifier is required when changing the gear oil in rear ends equipped with Ford traction-lock units.

What's In The Box

  • 3.31 Pinion Gear
  • 3.31 Ring Gear
  • Crush Sleeve
  • Pinion Nut
  • Pinion Bearings
  • Pinion & Carrier Shims
  • Pinion Seal
  • Ring Gear Bolts
  • Carrier Bearings
  • Gear Marking Compound
  • (1) Bottle of Motorcraft Friction Modifier
  • (2) Bottles of Royal Purple 75W140 gear oil

Installation Note

  • Although the Royal Purple gear oil has a friction modifier mixed in, it is still recommended that you use the bottle of Motorcraft friction modifier to supply your Super 8.8" IRS rear end with the proper amount of modifier.
  • LMR recommends the 75W140 viscosity for all 2015+ 8.8" differentials as it is appropriate for most climates, fuel economy, and performance.
  • 3.15 ratio differential is not compatible with 3.31, 3.55, 3.73, and 4.09 ratio gears. Use differential M-4240-M.


  • Fits 2015-2022 Mustang w/ Super 8.8" IRS Rear End

Ford Motorcraft Warranty - Click Here

  • Ford Mustang - 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022

California Residents:
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About This Brand

Ford Motor Company Genuine Parts, Motorcraft® Parts and Ford and Motorcraft Remanufactured Parts are all excellent choices when it comes to performance, longevity and value for your Mustang or SVT Lightning. And they’re all backed by a Ford Motor Company limited parts warranty*, so you know their parts you use are going to perform like they should. Put the same parts on your Lighting & Mustang that came from the factory!

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