Throtl Throwdown - May 2, 2026 Get Tickets! >

Richmond Ring and Pinion Gear Kit; 3.73 Gear Ratio (99-04 Mustang GT)Find parts that fit my vehicle

Item 66501G99
AmericanMuscle no longer carries the Richmond Ring and Pinion Gear Kit; 3.73 Gear Ratio (99-04 Mustang GT). Please check out 1979-1993 Foxbody Mustang Drivetrain for an updated selection.
Shop Owners Save More! Sign up for our dealer program

    Product Information

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

    Features

    • Exceptional Quality
    • Handle Extreme Torque Applications
    • First-Run, Never Recycled Materials
    • 3.73 Gear Ratio
    • 8.8" Ring Gear Diameter
    • 2-Year / 100,000 Mile Warranty
    • Fits 1999-2004 GT Mustangs

    Description

    Better Acceleration. If you need to upgrade your 8.8" rear end gears, look no further than the Richmond 3.73 Gears. You'll be able to acceleration faster, leave the line on a dime and get into the power band quicker in your New Edge Pony. Being one of the highest quality gears on the market, you can't go wrong with Richmond in your high performance Mustang.

    Superior Quality. Manufactured right in the United States, Richmond Gear uses only the highest standards to produce the highest quality gears in the industry. Inspected and scrutinized to deliver gears with acceptable tolerances, durability and fit, Richmond ensures only the best in machining, finishing and heat treating of their drivetrain components.

    Recommended Upgrade. When changing the gear ratio of your Mustang's rear differential, the calibration of your speedometer will no longer be accurate and will display the wrong speed. However, you can easily fix this annoying issue with a Tuner or Recalibration Tool (sold separately).

    Installation Notes. An Installation and Bearing Kit is highly recommended by most installers, especially on high mileage Mustangs. Please see ordering options above.

    Warranty. Richmond Gears is so confident in the high quality of their ring and pinions that they are backed by a 2-Year / 100,000 Mile No-Nonsense Warranty.

    Application. These Richmond 3.73 Ring and Pinion Gears will fit all 1999 to 2004 GT Mustangs equipped with an 8.8" rear end.

    Technical Note. Installation costs will vary, but a good rule of thumb is between $250 and $300. Be sure to work with a reliable shop that you trust for installations. You can also save money on your installation labor by having your Trac-Lok rebuilt at the same time your gears are installed. See ordering options above. Note, a 28-spline S-Spring will be required for 28-spline Mustangs (sold separately) if you opt for the Trac-Lok rebuild.

    CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

    Installation & What's in the Box

    Installation Info

    Installation Time

    (approx) a Day

    Difficulty Level:

    Mechanical expertise or professional installation required.

    Installation Guides

      No guide available for this part yet.

    What's in the Box

    • (1) Ring Gear
    • (1) Pinion Gear

    Tech Specs

    Approximate RPM for 1999-2004 GT


    Manual
    Gear@25 MPH @35 MPH @45 MPH @55 MPH @65 MPH @75 MPH
    1388854436998   
    2230132214141506159816902
    3151821262733334039484555
    4115016102070253129913451
    578210951480172120342347


    Automatic
    Gear@25 MPH @35 MPH @45 MPH @55 MPH @65 MPH @75 MPH
    1326745735880   
    2178324963209392246365349
    3115016102070253129913451
    480511271449177120932416
    4.9

    Customer Reviews (26)

    Questions & Answers

    No questions about this product yet. Ask the First Question