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EXCEL from Richmond Ring Gear and Pinion Kit - 3.90 Gears (05-09 GT, GT500)

Market Price $186.39 You Save 12% ($21.44)
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  • Item 21527G05
  • MPN# F88389

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Ship to: Ashburn - 20149
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    Features & Details

    • Superior Quality
    • 3.90:1 Gear Ratio
    • 8.8" Ring Gear Diameter
    • For Street or Track Use
    • Made in the USA
    • Fits 2005-2009 GT, Bullitt and Shelby GT500 Mustangs
    Improve Off The Line Acceleration. If you are still running the low ratio gears your V8 Mustang originally came with from the factory, you are probably finding it hard to get your pony up and moving. This is because most 2005-2009 Mustangs were equipped with 3.31 or 3.55 gears, which work very well for the fuel conscious daily commuter, but not for the spirited driver who wants jack rabbit like acceleration. By upgrading to a set of higher ratio 3.90 Richmond Excel Gears your Mustang will enter into its power band sooner which will help to improve low end torque and give you the quick off the line acceleration you're craving.

    Superior Quality. Richmond proudly manufactures their Ring and Pinion Gear Sets right here in the USA. Using state-of-the-art manufacturing processes and extensive quality control testing, Richmond produces a superior quality Ring and Pinion Gear Set at an excellent price. Richmond is so confident in the quality of their products that they back them with a 6 month, 50,000 mile no-nonsense warranty.

    Recommended Upgrade. Please note that when changing the gear ratio of your Mustangs rear differential that the calibration of your speedometer will no longer be correct and will display the wrong speed. However, you can easily fix this annoying issue with a Ford Racing Speedometer Recalibration Tool (sold separately).

    Application. This 3.90 ratio Richmond Excel Ring and Pinion Gear set will fit all 2005 to 2009 V8 Mustangs equipped with an 8.8" solid axle rear end, including the GT, Bullitt and Shelby GT500 models. A master bearing kit is recommended by most installers, especially on high mileage vehicles, see drop down option above.

    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 as your gears are installed, see drop down option above.

    Fitment: 2005 2006 2007 2008 2009 Details

    CA Residents: Warning: California's Proposition 65

    What's in the Box
    • (1) Ring gear
    • (1) Pinion gear
    Installation Info
    Tech Specs

    Approximate RPM for 2005-2009 GT

    Gear @25 MPH @35 MPH @45 MPH @55 MPH @65 MPH @75 MPH
    1 4065 5691        
    2 2405 3368 4330 5292 6254  
    3 1588 2223 2858 3493 4128 4763
    4 1203 1684 2165 2646 3127 3608
    5 818 1145 1472 1799 2126 2453

    Gear @25 MPH @35 MPH @45 MPH @55 MPH @65 MPH @75 MPH
    1 3873 5422 6971      
    2 2754 3856 4957 6059    
    3 1852 2593 3334 4075 4816 5556
    4 1203 1684 2165 2646 3127 3608
    5 854 1195 1537 1879 2220 2562
    Will it fit my Mustang?

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    Customer Reviews (4) Write a Review

    Overall Rating 2.2

    out of 5 stars

    Installation Time:Weekend

    Installation Cost:$250-$500

    • Performance Gain 4 4
    • Fit 3 3

    • 4/5

      Installation Time: Full Day

      August 28, 2018

      Nice in between

      These gears made a nice in between ratio for the car. Went from stock to 3.90 and still have good drive ability on the highway. 50mph it turns around 2500 rpm in 4th gear makes the car pull through a little faster which helps out with the cams 1st gear is still usable also.


      Year: 2005 Submodel: GT

      Helpful (0)

    • 1/5

      Installation Time: Shop Install

      Installation Cost: $250-$500

      June 07, 2017

      Excel 3.90 Gears

      Poorly manufactured. Gears make a lot of noise at any speed.


      Year: 2005 Submodel: GT

      Helpful (2)

    • 3/5

      October 14, 2010

      Richmond Gears 3.90

      The 3.90 gears really improve your acceleration and are the cheapest way to go faster without sacrificing too much fuel mileage/drivability. I was impressed by the quickness in which my order was received to my front door. However, after installing my 3.90 gears (making sure that both the pinion depth and backlash were correct) I noticed a whine. The whine did not subside after the break in period. I contacted AM who was very helpful and was instructed to speak with Richmond. Richmond did not really do anything to help me and hopefully the gears hold up. So far noise is the only problem. If I could do it again I would purchase Ford Racing gears.

      Bill Henry

      Helpful (5)

    • 1/5

      January 09, 2010


      Good ratio...VERY NOISY at cruise...and yes it is set up right ..pattern was perfect......replacing with FORD Gears....also Motive Kit for 8.8 did not include any small shims....only 14's and 30's.

      chris s

      Helpful (5)

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