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Motive Gear Performance Plus Ring and Pinion Gear Kit; 3.73 Gear Ratio (79-85 V8)

Item 21107G87
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Ship to: Ashburn - 20149
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      Product Information

      Features, Description, Reviews, Specs & Installation


      • Superior Quality
      • CNC-Cut from 8620 Gear Steel
      • 3.73 Gear Ratio
      • 7.5" Ring Gear Diameter
      • For Street or Track Use
      • Fits 1979-1985 V8 Mustangs


      Improve Performance. Wake up your V8-powered pony for faster acceleration off the line with a set of 3.73 Motive Performance Plus gears. A steeper set of gears will get you into your power band faster for faster launches and more punch off the line.

      3.73 Gear Ratio. 3.73 gears are a great combination of performance and fuel economy that's ideal for a daily-driven 'Stang that sees a lot of highway time. If you put a lot of miles on your Pony and don't want to increase your cost at the pump, a 3.73 ratio will still give you the added acceleration you want without compromising fuel economy dramatically.

      Superior Construction. 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.

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

      Application. This Motive Performance Plus Ring and Pinion Gear set will fit all 1979 to 1985 V8 Ford Mustangs equipped with a 7.5" rear end. 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.

      Fitment: 1979 1980 1981 1982 1983 1984 1985 Details

      Motive Gear F7.5-373

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (14)

      Write a Review

      Ratings Summary

      4.9 out of 5 overall rating from 14 customers

      Installation Time: Shop Install

      Installation Cost: $100-$250

      • July 31, 2018

        4 1984 Other - JoseS Installation Time: Shop Install Installation Cost: $100-$250

        Mustang 84

        Since gears were installed, the change on car was great. A little noise on the gears.

        Helpful (3)
      • March 17, 2017

        5 1985 Other - AK

        Motive Performance Plus 3.73 Gears

        My fox is like a brand new car. It takes off a lot faster than it ever did with the stock gears. I recommend this for anyone who is interested in drag racing or if they just want a little more umph from the car. There was a slight decrease in gas mileage, but that's the price to pay when you want to go fast!

        Helpful (5)
      • February 17, 2011

        4 - Brad Coxe

        Woke the pony up!

        This was a great product. Made my V6 really fly.. Only thing I didn't like is that it didn't come with and spacers or any of the bearings or crush collar that are pretty much mandatory. I wouldn't recommend doing rhis yourself unless you are a very experienced tech with a hoist. Don't count on finishing it in 1 day either. Took 2 buddies and I 2 7 hr. Days with a hoist. Very pleased with the product thus far. Just doin the 500 mile break in.

        Helpful (6)
      • January 11, 2011

        5 2000 V6 - justin p

        big time must

        got this 3.73...came from factory 3.27...2000 v6 mustang 5sp... i only lost 300 rpms..65mph is now 2250 rpms..factory was 1950... definatly is a whole lot quicker getting into the "power band" also got the t-lok with thing i have done so far to this car..well other than getting the wireless tuner for it :) thanks AM !!

        Helpful (5)
      • March 24, 2010

        5 - JUNIOR

        REAL POWER

        373,perfect fit for my V6 The difference is much, now runs with more power with better acceleration THANK YOU AMERICAN MUSCLE

        Helpful (7)
      • February 19, 2010

        5 - Fabian Hug

        Great Mod

        Great mod albeit expensive with POSI, bearing kit and a $ 430 prof. installation. It was worth waiting and saving. It really gives a boost to your V6. After long search on Inet, AM provided the best prices for these parts.

        Helpful (6)
      • November 03, 2009

        5 - colleen hartman

        one word "awsome"

        put gears in,took just a few hours.Did the 500 mile break in.Now i race all over town! I love the new power.Thanks,American Muscle.Im glad i went with the 373,perfect fit for my daily driver!!

        Helpful (6)
      • May 29, 2009

        5 - Joe

        less slow!

        I had to rebuild the rear end of my mustang so I figured I would throw in some lower gears to get some more pep from my slow single port. I am very happy with the result, the acceleration is much better. The down side is that at 65mph im at 2500rpm (5spd). At least it keeps me from getting speeding tickets on the freeway.

        Helpful (6)
      • May 15, 2009

        5 - Nikky

        A must!

        This product is a definite MUST a long with the T-lock to V6 enthusiasts! If you want more bang for your buck, then this is surely your item!

        Helpful (4)
      • November 18, 2008

        5 - Keith

        One beefy ring

        Got this along with my T lock. Talk about one solid piece of equipment!

        Helpful (5)

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      Installation & What's in the Box

      Installation Info

      What's in the Box

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

      Tech Specs

      Approximate RPM for 1979-1985 GT

      Gear @25 MPH @35 MPH @45 MPH @55 MPH @65 MPH @75 MPH
      1 3876 5427 6977      
      2 2289 3205 4120 5036 5951 6867
      3 1100% 2142 2754 3366 3978 4590
      4 1150 1610 2070 2531 2991 3451
      5 771 1079 1387 1695 2004 2312

      Gear @25 MPH @35 MPH @45 MPH @55 MPH @65 MPH @75 MPH
      1 2761 3865 4969 6073    
      2 1687 2362 3037 3712 4386 5061
      3 1150 1610 2070 2531 2991 3451
      4 767 1074 1380 1687 1994 2301

      Will It Fit My Mustang

      • Other - 79, 80, 81, 82, 83, 84, 85

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