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Motive Gear Performance Plus Ring and Pinion Gear Kit; 3.90 Gear Ratio (05-09 GT)

Item 21102G05
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      Product Information

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


      • Superior Quality
      • CNC-Cut from 8620 Gear Steel
      • 3.90 Gear Ratio
      • 8.8" Ring Gear Diameter
      • For Street or Track Use
      • Fits 2005-2009 GT, Bullitt and GT500 Mustangs


      Improve Overall Performance. A set of Motive Performance gears will wake up your Pony and get it moving faster off the line. Steeper gears are a great way to lower quarter mile times and improve responsiveness without sacrificing driveability. 3.90 gears are perfect for the Pony that needs more than 3.73s but less than 4.10s, offering a great blend of performance and efficiency.

      Superior Construction & Precision Fit. These Motive ring and pinon gears are CNC cut from high grade 8620 gear steel, and factory lapped for precision fit. Each set is hardness tested prior to leaving the factory to ensure the highest quality. Unlike other brands, Motive Gears do not have a reputation for "gear whine".

      Recommended Upgrade. Changing the rear axle gear ratio will throw off the calibration of your Mustangs speedometer, but a Ford Racing Speedometer Recalibration Tool is an inexpensive way to fix this issue.

      Application. This Motive Performance Plus 3.90 Ring and Pinion Gear set will fit all 2005 to 2010 V8 Mustangs including the GT, Bullitt and GT500 models. A master bearing kit is recommended by most installers, especially on high mileage vehicles, see drop down option above.

      Attention 2010 and newer Mustang Owners. Starting in 2010 Ford changed the inner rear gear pinion bearing in all 8.8" equipped Mustangs. Because of this you will require a new 8.8" rear gear pinion bearing (Ford part# 9L3Z-4630-A) for proper installation, please 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

      Motive Gear F888390

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (10)

      Write a Review

      Ratings Summary

      4.2 out of 5 overall rating from 10 customers

      Installation Time: Weekend

      Installation Cost: $250-$500

      • April 26, 2019

        5 2005 GT - EddyVsr

        Very nice!

        I def feel a change! In combonation with the bama x4 :) . A lil whine around 60-70 so i keep it at 80 lol

        Helpful (2)
      • June 02, 2017

        4 2008 GT500 - Night500 Installation Time: Full Day

        New Ring Pinion

        The packaging leaves much to be desired. I had to send the first set back. The next set was better, but still not protected. The gears seemed to be of high quality and installed like all the info that I read. The motive support was excellent, much better than american muscle. They wouldn't even call me back with help.

        Helpful (3)
      • July 20, 2016

        4 2008 GT - TheyCallMeBill

        Great performance, little noisy

        First off, AM saying that the gears have no tendency to whine is a blatant lie. Everybody and their mother knows that MOST of these gears will whine, even if installed perfectly. It's just the way the teeth are cut. Every forum everywhere will say the same thing. Mine make a little noise, but it is barely even noticeable unless you know it is there. The gears do provide some more grunt off the line, and make third gear usable coming out of corners. With the 3.55's, (I have an 08 GT), 40mph in third is useless, now it actually pulls pretty hard. Definite improvement over the factory ratio, but not quite as high revving as the 4.10's. I would choose the 3.90's again if I had to do it over. I paid $250 for install. Talk to the local drag strip guys and they will know a guy who installs these for half the price that shops do for the same quality of work. I was quoted $4-500 by all the shops in my area.

        Helpful (7)
      • February 15, 2013

        5 2008 GT - Dantheman490 Installation Time: Shop Install Installation Cost: $250-$500

        Great ratio, no whine

        I had this installed at a shop who has been doing gears for years because I have had no experience with it and didnt want to risk it. I installed it with the installation kit (which didnt have enough shims, american muscle nicely compensated me for trouble, great customer service) and a steeda diff cover amsoil fluid. I have had no whine and nothing but great acceleration and still maintain a decent rpm at highway speed

        Helpful (6)
      • March 23, 2011

        3 2009 GT - ben


        This is an awesome gear range. Made up for my bottom end loss from bigger tires without killing any top end. Only issue is a whine with speeds above 35, not horrible but not comfortable for long cruises.

        Helpful (6)
      • July 14, 2010

        3 - Matt


        Had gear professionally installed, greater acceleration and higher rpms, unfortunately the gear whines, would recommend ford racing, but they dont make a 390 so i chose motive because i wanted a 390, ill live w it

        Helpful (3)
      • June 02, 2010

        5 - chalmers

        perfect gear

        great gear not to low like 410s but still feels better then 373s.. i had gotten a rebuild kit with the gears.. i have not had any whine unless in reverse..

        Helpful (4)
      • December 05, 2009

        3 - david


        good compromise from 4.10s but have a tendency to whine.

        Helpful (3)
      • September 10, 2009

        5 - Brian

        better than 4.10s imo

        Went from stock to 4.10s. that lasted about a year. Decided to go down to 3.90s. They are definatly a much more street friendly gear, but still get up and move! 3rd redlines at about 85, and 4th is around 115, so you'll definatly still have plenty of oomph to blow past the slow traffic on the freeway-

        Helpful (8)
      • October 09, 2007

        5 - Travis

        Great get up and go.

        I feel that these are the great in between gears to have. I didn\'t want 3.73\\\'s but I didn\'t want 4.10\\\'s either. You will get a great improvement when you hit the throttle.

        Helpful (5)

      Questions & Answers (1 answers)

      1 Top Rated Question

      I am looking at the Motive Performance Plus 3.90 gears for my 2008 GT500. Is the pinion depth stamped in the face of the pinion? Do you have any of the setup tools required for installation ? Thanks Night500

      • The Motive Performance Plus 3.90 Gears would not have the pinion depth stamped on them. We do not carry any install tools for these gears at this time.

      Helpful (0)
      Post Your Question

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) Ring gear
      • (1) Pinion gear

      Tech Specs

      Approximate RPM for 2005-2010 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

      • Bullitt - 08, 09
      • GT - 05, 06, 07, 08, 09

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