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Ford Performance Traction-LOK Limited Slip IRS Differential - 34 Spline 8.8 in. (15-18 GT, EcoBoost, V6)

Market Price $203.99 You Save 12% ($25.00)
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  • Item 388769
  • MPN# M-4204-M

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    Features & Details

    • Put the Power to the Pavement
    • 8.8" IRS Limited Slip Differential
    • Factory OEM Replacement
    • Genuine Ford Racing Part M-4204-M
    • Requires 34 Spline Axles
    • Designed for Use with 3.31, 3.55 & 3.73 Super 8.8" Gear Sets
    • Fits 2015-2018 GT, EcoBoost and V6 Mustangs
    Limited Slip Differential. This Ford Racing 8.8" 34 Spline Traction-LOK Limited Slip Differential is a direct fit replacement for your IRS equipped S550 Mustang. A Limited Slip Differential (LSD) sometimes referred to as a "Posi" will allow both rear wheels to put the power down on the pavement giving you better traction and more impressive burnouts.

    Recommended Upgrade. This Ford Racing Traction LOK Limited Slip IRS Differential was specifically engineered for use with Ford Racing Super 8.8" IRS Gear and Pinion Sets, including 3.31, 3.55 and 3.73 gear ratios. Sold separately. Not for use with 3.15 gears.

    Application. This Ford Racing 8.8" Limited Slip Differential is the same original equipment that came standard on 2015-2018 GT, EcoBoost and V6 Mustangs. It is designed for use with independent rear suspensions (IRS) and requires the use of 34 spline axles.

    Technical Note. This Limited Slip Differential requires 4-ounces of CM-19546-A1 friction modifier with initial fill, it is recommended to use differential installation kit M4210B3.

    Fitment: 2015 2016 2017 2018 Details

    What's in the Box
    • (1) IRS Limited Slip Differential
    Installation Info
    Tech Specs
    Will it fit my Mustang?

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    9 Questions / 6 Answers

    Ask a Question

    I have a base model 2016 GT is this all I require to swap my gears from 3.15 to 3.55?


    • Hey Arturo, This differential is actually designed to work with steeper gears it isn't gears themselves. To upgrade to a 3.55 gear for your 15gt you would need item# 389949 which are not only the gears but the differential housing and differential to complete the entire install. Now if you wanted to you could get the ring and pinion separate, item#384402 but you would at least need one of these Ford differentials M-4204-MT or M-4204-M in order to complete the installation. And if you plan on making your mustang a high mileage car you would need a bearing a seals kits with the ring and pinion.


    Helpful (1)

    I have a 2017 v6 mustang. I want to move up to 3.73 gears, will this fit with the 3.73 gears for a v6? If not, what will I need to fit the 3.73’s?


    • The Ford Performance Traction - LOK Limited Slip IRS Differential is compatible with 3.73 gear sets.

      Rob D

    Helpful (0)

    Hey I have a 15 gt 6speed and I think my differential is getting bad it has play in it and bump every Time i let off the clutch. So I'm going to change this out and see . Will this work with my car with 3:31 in it and is it a straight forward install


    • The Ford Performance Traction - LOK Limited Slip IRS Differential will work with 3.31 gears. While the install can be pretty straightforward, we recommend professional installation of this differential.


    Helpful (0)

    Hi I think I have a worsen in my car - can I straight swap it for this one? thanks


    • The Ford Performance Traction - LOK Limited Slip IRS Differential will be a direct fit replacement for all 15-17 Mustangs with a 34 spline 8.8 rear, including those equipped with Torsen differentials.

      Rob D

    Helpful (0)

    Will this fit on my 2017 f150 with the 8.8 34 spline rear end


    • The Ford Performance Traction - LOK Limited Slip IRS Differential is specifically designed to work with the 2015-17 Mustang GT's and will not work properly with your 2017 F-150.


    Helpful (0)

    Will this work on a mustang ecoboost that's gonna be converted to 3.55's.


    • Yes, this works with 3.31, 3.55 & 3.73 gears.


    Helpful (0)

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    Customer Reviews (2) Write a Review

    Overall Rating 5.0

    out of 5 stars

    Installation Time:Weekend

    Installation Cost:$250-$500

    • Performance Gain 5 5
    • Fit 5 5

    • 5/5

      Installation Time: Full Day

      January 23, 2018

      Worked well for rear ends change

      I have a 2017 Ford Mustang V6 with a 6 speed manual transmission. The car came with 3.15 rear ends, I decided to change them to 3.73s. You cannot use the factory differential (new gears are too big), so I bought this differential, new gear set, bearings kit, and axle seal kit, all from American Muscle. A driveline shop did the install in 1 day. I'm very happy with the results. Had no issues with the parts!


      Year: 2017 Submodel: V6

      Helpful (3)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $250-$500

      October 22, 2015

      Worth every penny

      The process of getting the parts and advice needed to upgrade my gear ratios was priceless. I have total felt the difference in the gears. I am extremely happy with my mod. American Muscle customer for life!


      Year: 2015 Submodel: Ecoboost California

      Helpful (2)

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