Free Shipping On Orders Over $49. Details

Talk to a Mustang Enthusiast
M-F 8:30A-11P, Sat-Sun 8:30A-9P
Win $5,000 For Your Mustang! Enter Daily

Motive Gear Performance Plus Ring Gear and Pinion Kit - 3.90 Gears (99-04 GT)

Market Price $297.99 You Save 12% ($35.59)
Our Price


FREE Shipping

  • Item 21102G99

Will this fit your Vehicle?

Change Vehicle Help?
In Stock Ships same business day.
Ship to: Ashburn - 20149
Sorry, please enter a valid US or CA postal code
We're sorry, zip can't be updated at this time.
    Create a list
    Add to New List

    Saved - View your saved items

    We're sorry. We couldn't save this product at this time.

    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

    MPN# F888390

    CA Residents: WARNING: Cancer and Reproductive Harm -

    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?

      Customer Photos (1) Submit Your Photo

      View 1 Photo

        Questions & Answers (3)

        3 Top Rated Questions

        Fitment says will not fit my 01 Cobra. But down in the description or below it says fits all 8.8 of ear ends. Is there something different about my cobra 8.8 that I dont know about? And why does your descriptions contradict one another?

        • We apologize for the confusion, this gear kit will work with your 2001 Cobra Mustang and you will not have an issue getting this installed. We will be updating our site as well to reflect this as well.

        Helpful (0)

        Are these gears good for a daily driver? I drive 25 miles to work at 70-80 mph

        • The Motive Performance Plus 3.90 Gears can be used for a car that is daily driven, the rpm range for that speed will increase because of the gear size, but it can be used without issue.

        Helpful (0)

        What kind of oil is recommended for these gears?

        • The type of oil that is recommended for these gears will vary. If you street, daily drive, or live in a warmer climate you will want to purchase 75w90. If you live in a colder climate or drag race your Mustang, you will want to use 75w140.

        Helpful (0)
        Post Your Question

          Customer Reviews (18) Write a Review

          Overall Rating 4.6

          out of 5 stars

          Installation Time:Weekend

          Installation Cost:$250-$500

          • Performance Gain 4.818182 4.8
          • Fit 4.727273 4.7

          • 4/5

            November 13, 2018


            These gears are top quality. I heard ford performance gears were the only ones that didn’t whine, but I wanted just a bit more than the 3.73 they offered. These gears do have a bit of whine especially at cruising throttle in 4th but really not that bad. Car does pull a noticeable amount harder, definitely like the 3.90


            Year: 2001 Submodel: GT

            Helpful (3)

          • 5/5

            February 20, 2018

            Spicey Talako

            I received my items in a timely manner, and I am just waiting to find a quality shop to install my gears, so I can go and have some fun.


            Year: 2001 Submodel: Cobra

            Helpful (5)

          • 5/5

            Installation Time: Weekend

            November 18, 2017


            This is the gear that every street driven Cobra needs, it has awakened my 03 Vert like nothing else I have done and still keeps it in a decent range when driving at speed on the Interstate... It has drastically improved launch and E.T. and just makes the car feel totally different. The Motive Gear set has proven to be strong enough to hold anything I have thrown at it with nearly 700 rear wheel HP and 600 plus torque.. I installed the gear set and a new clutch and pressure plate by myself over a weekend but don't recommend anyone with less than an extensive knowledge of the Terminator and advanced mechanical skills attempt this on your own. I do recommend anyone looking at a 3.73 gear give the 3.90 a look...


            Year: 2003 Submodel: Cobra

            Helpful (5)

          • 5/5

            Installation Time: Full Day

            November 11, 2017

            great gears!

            Did an 8.8 swap in my v6 about 2years ago and decided i wanted to have some more get up and go. Rebuilt the entire differential, swapped the gears, rebuilt the clutch. These gears are great! Put 500 miles on them to break them in, and my car gets up a lot faster now. No gear whine or noise. Perfect for anyone who wants a little more than 3.73 but not as much as the 4.10


            Year: 2003 Submodel: V6

            Helpful (5)

          • 5/5

            Installation Time: Shop Install

            Installation Cost: $500-$1000

            June 19, 2017

            Gear set

            Looks to be a real nice set of rear gears if and when i get them installed,waiting on a part to arrive still. These are going to be the best of both worlds if you want a little quicker acceleration and mire power in every gear. 4.10 and up are more for just drag racing, these with give you good top speed and good pick up. Its costing me 750$ to have them installed but its by a pro who is also putting in everything new,axles,diff,bearings,seals,everything.


            Year: 2004 Submodel: GT

            Helpful (6)

          • 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 (7)

          • 5/5

            February 23, 2017

            3.90 motive gear

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


            Year: 2004 Submodel: GT

            Helpful (6)

          • 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 (7)

          • 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 (7)

          • 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 (6)

          • 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 (6)

          • 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 (9)

          • 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 (6)

          • 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 (7)

          • 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 (7)

          • 3/5

            December 05, 2009


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


            Helpful (5)

          • 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 (8)

          • 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 (6)

          Related Mustang Categories