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Yukon Gear 8.8 in. Duragrip Posi Rear Differential w/ 31 Spline 5 Lug Axles (99-04 GT, Mach 1)

Market Price $702.97 You Save 12% ($80.87)
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$622.10 (kit)

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  • Item 393820
  • MPN# 393820

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    Features, Video & Details

    • Put the Power to the Pavement
    • 8.8" Limited Slip Differential
    • Heavy Duty Nodular Case
    • Forged 4320 Internals
    • Yukon 31 Spline 5 Lug Axles Included
    • Fits 1999-2004 GT, Bullitt and Mach 1 w/ an 8.8" Differential Housing

    Review & Installation Video

    Review & Install Video

    Put the Power to the Pavement. Boost the performance and improve the road handling of your New Edge Mustang by upgrading to a Yukon DuraGrip Posi Rear Differential. This kit includes an 8.8in 31 Spline DuraGrip Posi Differential, a pair of 31 spline 5 Lug Axles and all the bearings and shims required for installation. This Yukon kit is ideal for those GT, Bullitt and Mach 1 owners who are looking to upgrade their stock differential and axles for better traction and more impressive burnouts.

    Posi Rear Differential. The DuraGrip Posi Rear Differential features a case constructed from a heavy duty nodular iron and boast forged 4320 steel internals and composite clutches for dependable heavy duty performance and long life.

    31 Spline 5 Lug Axles. Stronger than OEM, Yukon Gear manufactures their 31 spline 5 lug axles from high quality 1541H alloy steel for superior strength. They use a rolled spline process that produces an axle spline that is up to 30% stronger than standard cut splines.

    Durable Alloys. The parts in this Yukon Gear and Axle kit are built from high quality, heat-treated metal alloys for long-term durability. Top quality ensures extended use before needing to replace the parts. This complete axle kit includes everything you need for optimal road handling.

    Application. This Yukon Gear 8.8 in. DuraGrip Posi Rear Differential Upgrade Kit with 31 Spline 5 Lug Axles is designed for 1999 to 2004 GT, Bullitt and Mach 1 Mustangs equipped with a 8.8" rear differential housing.

    Technical Note. 1986-2004 V8 Mustangs came factory equipped with 28 spline axles, except for 2003-2004 SVT Cobras which were 31 spline. You will need to reuse your factory 8.8” gear set, or upgrade to a set of our 8.8" rear gears required for this Limited Slip Differential. No aftermarket gears are included. For normal driving conditions we recommend you use 75W 90 rear gear oil. This will give you the same oil weight as factory. For colder temps or race use try 75w 140.

    Fitment: 1999 2000 2001 2002 2003 2004 Details

    What's in the Box
    • (1) 8.8" Limited Slip Differential
    • (2) 31 Spline 5 Lug Axles
    • Carrier Bearings
    • Carrier Shims
    • Axle Bearings
    • Seals
    • Studs
    Installation Info
    Tech Specs
    Will it fit my Mustang?
    • Bullitt - 01
    • GT - 99, 00, 01, 02, 03, 04
    • Mach 1 - 03, 04

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    4 Questions / 5 Answers

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    Does this come with ALL bearings and seals required for installation? Or do I also need to buy a bearing and seal kit?


    • The will come with the Yukon Gear 8.8 in. Duragrip Posi Rear Differential w/ 31 Spline 5 Lug Axles will come with the hardware to install the differential. You will need to purchase the additional ring and pinion install kit which will include shims to install your gears back into your rear.


    Helpful (0)

    Stupid question but would this fit an automatic 2000 Mustang Gt?


    • Hello! The Yukon Gear 8.8 in. Duragrip Posi Rear Differential w/ 31 Spline 5 Lug Axles will fit on a automatic 2000 GT


    Helpful (0)

    Can this kit be used to convert a 99-04 V6 to a 8.8" rear end, assuming I acquire an 8.8" rear end housing? Is the driveshaft connection point the same or will that need to be swapped to one compatible with the 8.8" rear end? If driveshaft needs to be changed which one is going to be compatible with the T5 5-spd in my V6?


    • All this stuff fits in a 8.8 no problem.


    Helpful (0)

    So what ratio of ring and pinion are with this differential or do we have to use our own? (2000 v6 Mustang with GT 8.8 in. conversion)


    • You can use your old ring and pinion as long as it is an 8.8 rear end. I would suggest going to a 3.73 ratio. This setup is heavier than stock. You will feel a slight loss of power due to drivetrain weight. I love the 3.73... You can't go wrong with it.


    Show 1 more answer Helpful (0)

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    Customer Reviews (8) Write a Review

    Overall Rating 4.5

    out of 5 stars

    Installation Time:Full Day

    Installation Cost:$500-$1000

    • Performance Gain 4.375 4.4
    • Fit 5 5

    • 5/5

      Installation Time: Afternoon

      February 19, 2018

      Best Value Out There And It Is SOLID !

      This Yukon Gear package might be one of the best values on the market. For $622 you get the best 31 spline axels out there (a $350.00 value) along with a top notch posi spring/clutch diff. (a $500.00 value) and all the installation parts (bearings, shims, seals, ring bolts). All told, you are getting about $1,000 worth of top notch upgrade for $622.00. If you plan to put a set of gears or a new diff in your rear, you should get this outstanding bundle and get yourself set up with a 31 spline rear end. Another thing to keep in mind if you cant decide between a sping/clutch diff. like this Yukon or a Torsen set up like the Eaton TrueTrack... The Yukon spring/clutch can be rebuilt if you torch it later on down the road. If you damage a TrueTack, torsen, your only option is to toss it out. If you like, you can also put heavier sprints into your Yukon diff.


      Year: 2001 Submodel: GT

      Helpful (1)

    • 4/5

      Installation Time: Full Day

      February 08, 2018

      if you are a do it yourself guy

      if you're a do it yourself guy give yourself plenty of time to get it done.. for the bad things there is no e-clipse with the package or no manuals on how to set it your homework before attempting but on the good side my car is a lot more torque.. but all i have to say is good job it fits good and performs well..


      Year: 2001 Submodel: GT

      Helpful (1)

    • 2/5

      Installation Time: Afternoon

      February 06, 2018


      Comes with oem timken bearings which I was surprised and happy about which is why it's 2 stars and not 1. The reason I will not go with this brand again is because at about 1000 miles the spider gears decided that they weren't having it and broke into pieces.


      Year: 2004 Submodel: V6

      Helpful (1)

    • 5/5

      Installation Time: Full Day

      January 30, 2018

      Yukon Install

      Have not had a chance to drive yet but impressed with quality thus far. Can’t wait to drive it. Yukon kit combined with Ford Racing 4.10 gears on my 2003 Mach


      Year: 2003 Submodel: Mach 1

      Helpful (1)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $500-$1000

      June 24, 2017

      Great buy

      For the price you can't beat it. I had some bad bearings so I decided to upgrade the rearend of my 04 GT. AM customer support was a little slack when I asked them did this kit came with all the bearings for the rearend which it doesn't. But besides that it's a great buy.


      Year: 2004 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      June 23, 2017

      Awesome product

      Just had this installed in my 2003 Mach 1 and I can say this was a great investment! Definitely can tell a huge difference from the stock 28 spline


      Year: 2003 Submodel: Mach 1

      Helpful (2)

    • 5/5

      Installation Time: Full Day

      April 14, 2017

      Much better than Ford LSD

      I installed this in my 99 5spd GT. My factory LSD was shot and so where my axle bearings. I went through slot trying to get rid of clutch chatter. My biggest mistake ever was changing fluid brands. Put only Royal Purple 75-90 and only Ford brand LSD fluid, I put 2 bottles of Ford posi fluid. Car always launches straight with equal wheel spin. I tried everything the Yukon techs told me for months. Nothing worked. I broke it in with R.P. and it was perfect. At 500 miles I swapped in Lucas synthetic.... Mistake! So was conventional oil. Clutch chatter to the point it sounded like gears were chewing themselves. Put R.P. back in and it and it is super quiet.. I recommend a larger diff cover to allow more oil capacity. This posi displaces almost 3/4 of gear oil. I went from 3.23 to 3.73 Ford GT 500 ring and pinion bearing install kit also. Rear end is bulletproof now. I changed oil and inspected everything 5 times. Still looks like new a 2k miles, 10k I have zero issues. This is my D.D. too, still get 20-25 mpg


      Year: 1999 Submodel: GT

      Helpful (1)

    • 5/5

      December 23, 2016

      Yukon kit

      Its a great product. Very well built and heavy duty, also a good deal.


      Year: 2004 Submodel: GT

      Helpful (1)

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