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Alloy USA 8.8 Axles; 31 Spline 5 Lug (99-04 GT, Mach 1)

Item 18957
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Market Price $298.99 You Save 13% ($39.00)
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$259.99 (pair)

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      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • 1541H Alloy Steel
      • 31 Spline
      • 5 X 4.5" - Five Lug Design
      • 10 Year Warranty!
      • Driver and Passenger Side Axles Included
      • Fits 1999-2004 GT, Bullitt and Mach 1 Mustangs with 8.8" Rears


      Performance Upgrade. If your Mustang is heavily modded or running a forced induction setup, your stock 28 spline axles might be too weak to take the heat. These premium quality 1541H alloy steel axles have 31 splines to ensure all that power and torque is transferred straight to the pavement - where it belongs.

      Stronger than OEM. Manufactured from high quality 1541H alloy steel using a computer controlled induction heat treatment that results in a stronger, more durable axle shaft. Alloy USA uses a cold-formed rolled spline process that produces an axle spline that is up to 35% stronger than standard cut splines.

      10 Year Warranty. These Alloy USA axles come with a 10 year limited warranty to be free of defects in material and workmanship from the date of purchase. Some limitations do apply. Please see the full Alloy USA Warranty disclosure for details.

      Application. This pair of Alloy USA 5-Lug 31 Spline Axles are specifically designed for use on 1999 to 2004 GT, Bullitt and Mach 1 Mustangs that have upgraded to a 8.8" 31-spline LSD or Spool only.

      Application Note: 1986-2004 V8 Mustangs came factory equipped with 28 spline axles, except for 2003-2004 SVT Cobras which were 31 spline. All 2005 and newer V8 Mustangs come equipped with 31 spline axles.

      Fitment: 1999 2000 2001 2002 2003 2004 Details

      MPN# 12187

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (10)

      Write a Review

      Ratings Summary

      4.8 out of 5 overall rating from 10 customers

      • November 25, 2019

        5 2002 GT - DJW

        Great product.

        Great axles with excellent warranty. No problems with install.

        Helpful (0)
      • April 13, 2018

        4 2003 GT - RedfireRed


        Well made working good so far, they are a touch longer than stock so have to shim calipers slightly but very well made

        Helpful (8)
      • October 17, 2014

        5 2003 GT - Danwago

        Must have

        While putting in new 3.73 gears wanted to upgrade my limited slip differential, the Gt differential is a 28 spline 8.8in for $484.99 ...upgrade to the 31 spline which was half the cost plus these bad boys made it the same price as the diff alone plus my rear end is ready for anything I can throw at it. Thanks AM.

        Helpful (8)
      • October 17, 2014

        4 2002 GT - Dandaman779

        Great product

        This is a great quality set of axles... One of the only companies to offer a 10 year warranty. The only single complaint I have is they come with the cheaper koyo bearings... I expected them to use something made in USA but they are still great quality bearings don't let that keep you from buying them. One thing I did notice is these axles seem to be wider than stock... Maybe it's just me but had to grind a very slight amount off of the passenger side caliper bracket. I'm talking very slight. Wasn't worth the hassle of a return to me. Handles my 410hp gt without a problem

        Helpful (9)
      • September 21, 2014

        5 2002 GT - DBoi941

        Great Axles

        Great axles, Nice upgrade to my stang. Easy to install.

        Helpful (9)
      • October 23, 2013

        5 2000 GT - Drunkninja

        Rear end

        My car has 140k+ miles and I decided to install some 4:10 gears. Figured while I have it apart, I might as well replace everything the first time. Install went great and now my rear end is bullet proof.

        Helpful (9)
      • October 19, 2013

        5 2000 GT - Perry52D

        Excellent product

        I bought this with Ford Racing 4.10 gears and the posi trac differential. I Also purchased a 75mm throttle body and a bama tuner. I am 100% satisfied with everything I bought and installed. Great products, everything I have is a must have for a mustang. Very aggressive off the line and excellent throttle response. Thanks American muscle!!!!! I have and will always buy from American Muscle.

        Helpful (9)
      • October 18, 2013

        5 2004 GT - Runningstang2004

        Great Product

        These axles worked out great for my 31 spline up grade on my 04 gt.

        Helpful (9)
      • September 21, 2013

        5 2001 GT - Ohler248

        Fast shipping

        Bought these to beef up the rear end of my turbo mustang. Kind of like an insurance policy when launching with slicks.

        Helpful (9)
      • July 01, 2013

        5 2002 GT - Vault

        Rear end 2fast 2furious Saleen, movie car)

        When I bought this car it had been raced hard and the rear was toast. I upgraded to the 31 spline axles, ford diff,ford racing aluminum driveshaft and ford racing diff cover. The car is quieter and smooth on all launches. So far I am very happy. Also picked the axles because they were made in the US.

        Helpful (9)

      Questions & Answers (4 answers)

      4 Top Rated Questions

      How much power are these rated for? Im putting together a 400-500 whp build

      Do these axels come with c clamps?

      • These axles reuse your factory c-clips,

      Helpful (0)

      Do these axles use the factory rear knurl sized studs? Could you tell me what size they use either way? I would like to run longer studs.

      • These Alloy USA 8.8 Axles will use a 0.625 in. knurl wheel stud, just like OEM.

      Helpful (0)

      What should I stall with this axles? I have a stock 2000 Mustang GT, and I would like to know what other parts should I install to fit this axles to my Mustang. Should I install also another Driveshaft and Differential? I would like this part for track usage and daily drive, and I will make some power mods to the car. Thanks in advance!

      • You need a 31 spline differential. And to install the differential you need to purchase a gear install kit so you get new shims and carrier bearings... Driveshaft is not neccesary

      Helpful (0) Show 1 more answer
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      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (2) 31 Spline Axles
      • (10) Wheel Studs
      • (2) Outer Axle Shaft Bearings
      • (2) Seals

      Tech Specs

      • Splines: 31
      • Type: C-clip
      • Stud Pattern: 5 x 4.5"
      • Stud Type: Press in

      Will It Fit My Mustang

      • Bullitt - 01
      • GT - 99, 00, 01, 02, 03, 04
      • Mach 1 - 03, 04

      Fits 8.8" rear gears with 31 spline LSD or Spool only

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