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Motive Performance Plus 3.90 Gears (99-04 GT)

Market Price $219.97 You Save 9% ($20.00)
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  • Item 21102G99
  • MPN# F888390

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Features & Details

  • Superior Quality
  • CNC-Cut from 8620 Gear Steel
  • 3.90 Gear Ratio
  • 8.8" Ring Gear Diameter
  • For Street or Track Use
  • Fits 1999-2004 GT, Bullitt, Mach 1 and Cobra 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 1999 to 2004 V8 Mustangs including the GT, Bullitt, Mach 1 and Cobra 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: 1999 2000 2001 2002 2003 2004 Details

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

Approximate RPM for 1999-2004 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 3416 4782 6148      
2 1864 2610 3355 4101 4847 5592
3 1203 1684 2165 2646 3127 3608
4 842 1179 1515 1852 2189 2526
Will it fit my Mustang?
  • Bullitt - 01
  • Mach 1 - 03, 04
  • Cobra - 99, 01, 03, 04
  • GT - 99, 00, 01, 02, 03, 04

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Most Helpful Reviews


Like a whole new car! The break in period darn near killed me. Thought about pulling a Ferris Bueller haha

Helpful (1)

3.90 motive gear

Great performance, not bad on gas mileage, good price.

Helpful (1)

Overall Rating 4.5 out of 5 stars
Read All 13 Reviews

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Customer Reviews (13) Write a Review

Overall Rating 4.5

out of 5 stars

Installation Time:Weekend

Installation Cost:$100-$250

  • Performance Gain 4.833333 4.8
  • Fit 4.5 4.5

  • 5/5

    February 23, 2017

    3.90 motive gear

    Great performance, not bad on gas mileage, good price.


    Year: 2004 Submodel: GT

    Helpful (1)

  • 5/5

    September 25, 2016


    Like a whole new car! The break in period darn near killed me. Thought about pulling a Ferris Bueller haha


    Year: 2000 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Weekend

    January 27, 2012

    Excellent Ring and Pinion!

    I recommend these Motive 3.90 gears to anyone considering between 3.73 or 4.10 gears, this ratio is perfect for the T-3650 5 speed and even the T-56 6 speed manual transmission. Motive makes an excellent ring and pinion. I swapped out my old Motive 3.73 for these 3.90, Motive gears are made with great precision. The ring run-out was perfect and pinion depth (calculation) was spot on to the marking on the pinion head itself. Also, I would advise a bearing and shim installation kit towards your build, it's always "good insurance".


    Year: 2003 Submodel: Mach 1 New York, NY

    Helpful (3)

  • 5/5

    September 10, 2009

    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 (3)

  • 5/5

    June 02, 2010

    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 (2)

  • 5/5

    March 07, 2010


    The only word to describe these gears is crazy! They gave my '02 GT so much more life. I had a hard time deciding between 373s and 410s, so i just went with these and i am glad i did!


    Year: 2002 Submodel: GT

    Helpful (2)

  • 4/5

    Installation Time: Shop Install

    Installation Cost: $100-$250

    May 01, 2016

    Turn-up the stereo, then punch it!

    When I removed the IRS subframe last year, I took the Diff to Ronnie at Prime Time Racing on Summit Av in Greensboro, NC. He installed the Motive 3.90 gear for $250. With poly subframe bushings, Delrin upper / lower control arm bushings, aluminum Diff bushings front and rear and a number of other suspension goodies, I re-installed the IRS. I followed Ronnie's break-in procedure: cycle the rearend from hot to cool four times. I ran the car for 4 miles at 3K plus rpm, then 3 miles at less than 1500 rpm. I do have gear noise, but it is not what I call a "whine." It sounds like new sheet metal sliding back and forth at a medium to low frequency. SHMotorsports warns for this reason to use only Ford Racing gears. But like so many others have commented, 3.73 is not enough and 4.10 is a royal pain. This gear pulls like a supersonic freight train. As such, I normally start in 2ND gear without slipping the clutch and you can accelerate in 5th with some authority, but it is much more fun to grab a lower gear. My gas mileage dropped from 24/25 mpg to 21 mpg on the highway. I recommend this gear for highway and autocross, but not for daily driving because of the cost of fuel. I wish Ford Racing made the same ratio so Motive would not feel compelled to stick us with the high price.


    Year: 1999 Submodel: Cobra

    Helpful (1)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: $250-$500

    July 14, 2013

    Woke up my 4.6 more than any other upgrade

    This was a great investment. Went from stock 3.27's to these. My 99 cobra has never had so much useable power. I hit about 2700 rpm at 75mph with a T-45 tranny in 5th so it's still completely highway capable. This also helped minimize the cam lope I had while in gear at lower rpms. I will be needing new tires now though. Over all a great buy. One note is the shop I used didn't have the right size shims so it took a few days for install. Also u will need to adjust your tune to the new ratio or your speed-O will be off by quite a bit.


    Year: 1999 Submodel: Cobra Kansas City, KS, USA

    Helpful (1)

  • 4/5

    Installation Time: Shop Install

    Installation Cost: $100-$250

    July 09, 2013

    Excellent choice for a 99-01 Cobra

    I chose these gears for my 99 cobra and took them immediately on a 4300 mile road trip after the break in time. I felt that the 3k rpms at 85 was reasonable for the trip and I didn't notice much of a gas millage drop after the install. Performance wise these we killer for the bends and helped out my top end on my stang. I topped out at 172 on the autobahn (gps verified) with the aid of these gears where I wasn't able to get over 160 with the previous gears (long tubes also were added between runs). These gears made me want a t56 for my car because it feels like I have no overdrive now, 5th is VERY usable and the car still pulls like a train! The only thing I wasn't happy with is the price premium over the 3.73's/4.10's its a bit of a kick in the teeth by Motive. Very nice gear and minimal whine; I have aluminum bushings in the rear so I expected more.


    Year: 1999 Submodel: Cobra Cambridge, UK

    Helpful (1)

  • 5/5

    October 09, 2007

    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 (1)

  • 3/5

    December 05, 2009


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


    Helpful (0)

  • 3/5

    July 14, 2010


    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 (0)

  • 5/5

    Installation Time: Afternoon

    April 20, 2017

    Good upgrade with track proven results

    Before I installed these gears my 2004 GT auto was running consistant 14.0s with the occasional 13.90s pass with 99mph trap speed. My personal best was a 13.90 at 99mph with street tires and a 13.98 at 99mph with the MT ET drag radials (they are pretty heavy tire, 275/50/15). I installed thesse with the Ford Racing rebuild kit and was able to run a best of a 13.77 at 100mph with bald Mickey Thompson ET's. I'm hoping to get a few hundredths off with the fresh MT DRs that I have and will be moving to the Hoosier QTP radial as they are about 14lbs lighter each then the MTs. Hoping that loss of rotational weight will get me around a tenth off and crack into the 13.60s. Driving wise, this is my daily. With the stock 3.27s I was getting about 250-ish miles per tank. With the 3.90s I am now getting around 230-ish miles per tank. Went from about 22mpg to 20 mpg-ish. These do have a bit of a howl to them and I experience it mostly when daily driving from the 45-55 mph range while excelerating. I do not notice any noise while at the drag strip. Decel while daily driving or racing I notice no noise. Freeway speed of 75mph is about 2550 rpm. I did have these professionally installed for $300 and it took the shop about 3 hours. I definitely suggest thse to anyone that is looking for a decent street/strip gear that is not afraid of the chance of a little howl.


    Year: 2004 Submodel: GT

    Helpful (0)

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