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Roush Underdrive Pulleys (05-10 GT)

AmericanMuscle no longer carries the Roush Underdrive Pulleys (05-10 GT). Please check out 2005-2009 Mustang Underdrive Pulleys for an updated selection.
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AmericanMuscle no longer carries the Roush Underdrive Pulleys (05-10 GT). Please check out 2005-2009 Mustang Underdrive Pulleys for an updated selection.

Features & Details

  • Free Up 8 to 10 Horsepower.
  • Improves Fuel Efficiency
  • Two Piece Kit.
  • Black Finish.
  • Fits 2005 to 2010 4.6 GT Mustangs.
Free Up Horsepower. The Roush Underdrive Pulley Kit will allow you to gain more horsepower, gas mileage, and accessory life by using 25% less power than the stock pulley.

Quality Construction. This Roush 2-piece Replacement Pulley set is crafted from steel for durability and strength. They are completed in a black powdercoat finish for great looks under the hood.

Fitment. The Roush 2-Piece Underdrive Pulley Kit is designed for use on the 2005 to 2010 GT Mustang with the 4.6 SOHC V8 Engine and reuses the stock belt for installation. Not compatible with ROUSHcharged Mustangs.
What's in the Box
  • (1) Crankshaft Damper Pulley
  • (1) Water Pump Pulley
  • (1) Crankshaft Damper Bolt
  • (1) Alternator Bolt
Installation Info
Tech Specs
UnderDrive Pulley Specifications
Year/Model: 2005-2010 GT Manufacture: Roush Performance
Material: Steel Finish: Black
Crank Pulley: One Piece Crank SFI Certifited: Yes

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4 Questions / 7 Answers

Ask a Question

I have this kit on my car and the balancer went out can I buy just the balancer


  • At this time we do not offer individual components for the Roush Underdrive Pulleys. We would recommend contacting Roush directly for individual parts such as the balancer.


Helpful (0)

Will I need a tune? I'm running a diablosport right now


  • These underdrive pulleys will not need a tune.


Helpful (0)

Will I require a new serpentine belt or will I need to buy a new one?


  • The original belt worked for my 05 GT when I installed this kit.


Show 2 more answers Helpful (0)

Will a roush charger work with these pulleys? im wanting to buy a rouch charger soon. will these work with?


  • No. Under drive pullers will lower your boost.


Show 1 more answer Helpful (0)

Customer Reviews (11) Write a Review

Overall Rating 4.8

out of 5 stars

Installation Time:Afternoon

Installation Cost:0-$100

  • Performance Gain 4.222222 4.2
  • Fit 4.888889 4.9

  • 5/5

    Installation Time: Less than 1 Hour

    August 31, 2017

    Very good product worth the extra money for steel!

    works as it should and was easy install, follow directions and it should be a snap!


    Year: 2006 Submodel: GT

    Helpful (2)

  • 3/5

    Installation Time: Afternoon

    July 18, 2017

    Nice gain but can be an installation pain

    The gains are noticeable and right away in your throttle response. However, every other kit I've looked up comes with an installation bolt in order to draw in the harmonic balancer pulley enough for the factory bolt to go back in. It's nice that they provide a replacement for the factory bald but if I were to choose one or the other I would prefer an "installation tool" bolt and to use the factory one once it can bite. So long story short if you choose to go Roush be prepared to take your factory bolt to the hardware store match the threads and bring home a longer one to finish your installation properly and it won't hurt to grab a stack of washers just in case you need to make up for some room while you draw the pulley in.


    Year: 2006 Submodel: GT

    Helpful (2)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: 0-$100

    July 15, 2017


    These are great!! I had a Ford dealership install the kit. Very happy.


    Year: 2006 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Full Day

    May 26, 2017

    Because they are Roush Quality

    I bought Roush because they are steel and because I use Roush Parts for most of my mods. My Speed Shop warned me about using Aluminum and possible pitfalls. I didn't expect much if any performance gain as far as acceleration. Because of 4.10 gears my AC was running 30 degrees and below and my battery was charging at a very high rate. Battery was holding 12.79 Volts after setting over night. Now it's 35 degrees at the duct and the battery is holding at 12.5 Volts. Be sure you totally understand the directions they are good but could go into more detail if this is your first time pulley install. The pulleys accomplished what I was after. I am disabled so the install took extra time. I'm slow and cautious.


    Year: 2005 Submodel: GT

    Helpful (2)

  • 5/5

    Installation Time: Less than 1 Hour

    April 22, 2017

    under drive pulleys

    went with roush quality unit and proven company use same belt but did install new ford one with install every thing was apart all ready also did seal use ford rite fit have shop so had the puller and install tools easy job


    Year: 2009 Submodel: GT

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    January 29, 2016


    I have a 2005 mustang GT I recommend this Rouch underdrive pulley it's a good up grade I feel a big difference didn't take much to install.


    Year: 2005 Submodel: GT Fresno

    Helpful (2)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: 0-$100

    August 24, 2014

    Roush Underdrive Pulley

    Roush underdrive pulleys are really easy to put on and have a great fitment! I'm glad I went with this product and know that roush will never let you down with amazing materials and a professional finish. Recommend this product to anyone with a s197 stang!


    Year: 2007 Submodel: GT Los Angeles, CA, USA

    Helpful (2)

  • 5/5

    Installation Time: Less than 1 Hour

    June 06, 2014

    Easy to install

    After reading problems with overheating I was skeptical about ordering, but did it anyways. Installed in about an hour, only took that long because I had to go rent the tool to put new pulley on. After driving around town, car didn't overheat even with the a/c on in about 95 degree weather. Temperature stayed about the same as before. Have noticed steering is a bit harder, a/c is still pretty cold. As far as noticing more HP, can't say for sure because the same day I did the pulley I installed Kooks Headers.


    Year: 2005 Submodel: GT Hobbs, NM, USA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    April 27, 2012

    nice power adder for a quick install

    The install went very swiftly, especially having a helping hand. The first time around I installed a new OEM belt and that snapped on my way home, I would advise anybody that gets a new belt to get a size up (my mistake to not). Overall i'm very happy with the added horses the pulleys unleashed. The pony is pulling noticeably harder and to me seems like it has a meaner growl to her. I'd reccomend this to anybody that wants a nice install, clean fit, and quick power for under $250. Not having to see that huge piece of rust is a benefit to!!!


    Year: 2007 Submodel: GT Woburn, MA

    Helpful (6)

  • 5/5

    August 21, 2010


    Just installed took about 45 min. Noticed a big difference with throttle response. Recommend this product!!!


    Helpful (8)

  • 5/5

    December 12, 2009


    Just installed and can tell a big difference in throttle response and looks great too.


    Helpful (8)

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