1999-04 Mustang 8.8" 31 Spline Heavy Duty Rear Axle Kit 3.73 Gears

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  • Mustang 8.8" 31 Spline Heavy Duty Rear Axle Kit 3.73 Gears (99-04)
Mustang 8.8" 31 Spline Heavy Duty Rear Axle Kit 3.73 Gears (99-04)

Beef up your 1999-2004 Mustang's 8.8" rear end the right way with this heavy duty rear axle kit with 3.73 gears!

Item #LRS-4204SDK-E

Everyday Low Price: $1,099.99

Out of Stock 

Not Available for APO or Air shipping.

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  • Bullet Proof Your Rear End
  • Optimizes Traction
  • Improves Acceleration


  • Track-Ready Components
  • One Piece Forged Axles
  • 31 Spline
  • FRPP Carbon Clutch Disc Differential
  • Fits 8.8" Rear End

What's in the Box

  • (See Description Below For Components)

Product Description

1999-2004 Mustang 8.8 31 Spline Conversion with 3.73 Gears

So, you want to beef up your Mustang's 8.8" rear? How about a kit that gives you EVERYTHING you need to make it bullet-proof? We include everything you need to make your rear axle ready for severe service, be it on the drag strip or the road course!

Kit Includes:
- FRPP Carbon Clutch Disc 31 spline differential M-4204-F318C
- Hardened 31 spline 5 lug axles MOS-9903-31
- High Strength Steel 3" studs MOR-46180
- Ford Racing (FRPP) 3.73 gears M-4209-88373
- FRPP M-4210-B2 bearing kit
- Axle bearing & seal kit AK-1563
- Carrier bearing cap stud kit M-4034-A
- Heavy duty differential support/cover M-4033-G2
- Pinion flange LRS-4851A
- 75W140 Royal Purple synthetic gear oil

- Axles do not include ABS rings. Reuse factory ABS ring or replace with LRS-2189A.
- Does not fit IRS equipped Mustangs.

Due to Hazmat regulations, lubricants/fluids cannot be shipped to APO/FPO addresses.

Ford Performance Racing Parts - NO WARRANTY - Click Here

Speedometer Correction
After installation of rear gears, you will need to correct the speedometer. There are different methods to do this depending on year model.

1979-1995 Speedometer Correction - Click Here

1996-2017 Speedometer Correction - Click Here

Customer Photos (0)

Product Reviews (3)

out of 5 stars
5 stars
3 reviews
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3 of 3 REVIEWS
3 of 3 REVIEWS

5 Stars   Almost the perfect kit
By on 5/9/2014
I bought this kit and while everything about it was flawless. It did need some extra pieces that I had to buy that possibly should have come with the kit.

for instance, I needed these after I discovered my ABS rings where completely rusted into place on my old axles. http://www.latemodelrestoration.com/item/LRS-2189A/94-04-Mustang-Rear-Axle-Abs-Reluctance-Tone-Ring which clearly states you should buy these when replaceing your rear axles.

also the lugs are about 1.5" longer than your stock lugs so you will need to buy long lug nuts or in my case some high grade open end lug nuts. I guess the lugs are made for people that run all kinds of positive or negative wheel offset, but still a set of nuts would have been nice to have and would only add about 15 bucks to the kit.

Yes, I would recommend this item to a friend!

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5 Stars   All the Accelerations!
By on 4/13/2015
I got this whole kit installed professionally so I can't comment on the components other than they are trusted. No whine out of the gears, acceleration is solid now, throttle feel is amazing through every gear. This is the way mustangs should have came from factory. Mine is paired up with a 425HP supercharged 4.6 2 valve and it woke it up.

Yes, I would recommend this item to a friend!

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5 Stars   Exactly what I needed
By on 2/20/2015
Owner before me put 4.10 gears in the car. I opened up the rear cover and noticed the ring gear was flared out from not correctly setting the pinion which resulted in slack in the ring/pinion clearance. This package fixed everything and the new rear cover is incredible. Highly recommended.

Yes, I would recommend this item to a friend!

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Vehicle Applications

Ford Mustang - 1999 (99) - 2000 (00) - 2001 (01) - 2002 (02) - 2003 (03) - 2004 (04)

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