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SR Performance Underdrive Pulleys (Late 01-04 GT)

Market Price $159.99 You Save 13% ($20.00)
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$139.99

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  • Item 388722
  • MPN# 388722

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    Features, Video & Details

    • Gain Horsepower
    • Complete Kit
    • Durable, Lightweight Aluminum
    • Brilliant Polished Finish
    • Premium Quality
    • Fits Late 2001 to 2004 GT

    Review & Installation Video

    Review & Install Video

    Hey I’m Justin with AmericanMuscle.com, and I’m going to be breaking down the SR Performance underdrive pulleys, fitting the 4.6L V8 motor found in all 96-04 Mustangs. Engine accessories like the AC compressor, water pump and alternator can really rob your car of horsepower, a great example of how an accessory can really eat up is whenever you turn your car’s AC on, and instantly everything feels a little more sluggish. This is referred to as parasitic drag. The job of an underdrive pulley is to turn the different accessories at a different speed by using a different sized pulley, thus requiring less amount of energy from the engine to turn the accessory belt. This reduction in drag on the crank shaft will allow the engine to work more efficiently, and should equate to more power at the rear wheels. The SR Performance kit does include a brand new crank pulley, a new water pump pulley which will differ depending on your year, a new alternator pulley, and all the hardware and spacers needed for the install. All 3 pulleys have been made from lightweight aluminum and feature a nice bright polished finish, which should definitely help the appearance side of things underneath the hood. As far as the install is concerned, it really shouldn’t be all that bad, ideally, you should have a torque wrench on hand before you get started, as well as some high temp RTV sealant and a breaker bar for that crank pulley. Again this isn’t the hardest job, but you should expect to spend about 2 hours getting everything bolted up. If you should have any problems, you can always reference the detailed instructions along with pictures located on this product page. So if you’re looking to take some of the drag off your accessories, in turn freeing up some horsepower, and improving your throttle response, then you should definitely check out these pulleys from SR Performance, available right here at AmericanMuscle.com

    Untap Hidden Horsepower. Add some more bite to your GT's bark by reducing the amount of power you're losing to accessories and A/C. When you install this underdrive pulley kit, you'll free up up to 15 horsepower - and it's pretty much all gain and no pain, since you won't sacrifice your charging characteristics or A/C to do it.

    Premium Quality. Don't settle for inferior parts. These premium quality pulleys are made from lightweight aluminum for durability and performance. Made using precise, state-of-the-art CNC manufacturing, you can count on these pulleys to perform at the highest level.

    Easy Installation. This Underdrive Pulley kit installs quickly and easily in under 2 hours with no modifications required.

    Application. These underdrive pullies are designed for the Late 2001 to 2004 GT with the short water pump pulley with a bowed in face. Re-uses factory serpentine belt.

    Technical Note. Midway through the production run for the 2001 model year Ford changed the design of the water pump on the 4.6L engine. The older style pump produced from 1996 to mid 2001 had a longer shaft. In January of 2001 the design of the pump was changed to a shorter shaft. This necessitated a change in the design of the pump pulley.

    Click here to see pictures of the different pulley styles.

    Fitment: 2001 2002 2003 2004 Details

    What's in the Box
    • (1) Crank Pully
    • (1) Water Pump Pully
    • (1) Alternator Pully
    • (2) Spacers
      Hardware included:
    • (4) Bolts
    • (3) Washers
    • (1) Crank Key
    Installation Info
    Tech Specs
    Underdrive Pulley Specifications
    Year/Model: Late 01-04 GT Manufacturer:
    Material: Aluminum Finish: Polished
    Crank Pulley: Piggyback SFI Certified: No
    Will it fit my Mustang?
    • GT - 01, 02, 03, 04

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    4 Questions / 4 Answers

    Ask a Question

    Wil these pullies be ok with stage 2 cams?

    BruceB

    • The SR Performance Underdrive Pulleys will work fine with Stage 2 camshafts.

      AshleyK

    Helpful (0)

    Do these piggyback on the harmonic pulley?

    DarrellH

    • Thank you for your question about the SR Performance Underdrive Pulleys (Late 01-04 GT). The crank pulley does piggyback on the harmonic balancer pulley.

      AMRich

    Helpful (0)

    When will AM have 99-04 V6 mustang underdrive pulleys? I would like a set, but the only set is $350 from some sketchy website.

    ScreamingGoat43

    • We are constantly getting new products on our site, so keep checking back!

      AshleyK

    Helpful (0)

    how much does this kit change change the ratio at the crank? What is the diameter of the stock crank pulley and what is the diameter of the BBK? Thanks.

    Johns2004GT

    • It does not change the ratio at the crank the ratios are changed at the power steering, air conditioning, alternator and smog pump if you have one. They supply a pulley to maintain the rpm at the water pump so you don't over heat. And the HP gain is a bout 5 to 8 HP. Get a tuner or a CAI or both if you really want to feel a increase in power when you hammer it down!!!

      fasteddie64

    Helpful (0)

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    Customer Reviews (27) Write a Review

    Overall Rating 4.3

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:$100-$250

    • Performance Gain 4.047619 4.0
    • Fit 4.095238 4.1



    • 5/5

      Installation Time: Afternoon

      January 20, 2018

      Underdrive Pulleys

      Easy install, great look under the hood and noticeable gain on throttle. I would recommend to anyone looking for mods on a budget.

      ChrisYoungblood

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      Installation Time: Less than 1 Hour

      December 25, 2017

      Mustang

      Great little mod to gain just a little more power!

      Matthew

      Year: 2002 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      October 20, 2017

      My favorite mod

      Install was fairly easy, but I was bummed that I had to keep the old crank pulley attached to the new one. It would be nice to have less rotational mass. I got noticeable acceleration gains immediately from low rpm all the way up. This is an excellent mod and power increase for the money. The only problem I experienced years later was a little belt slippage and squeaking but that stopped after I put rubber conditioner on the belt.

      Chasing300

      Year: 2001 Submodel: GT

      Helpful (0)

    • 4/5

      Installation Time: Weekend

      October 13, 2017

      As Advertised

      Like always product came quickly and in good shape. Directions were good. Unfortunately removing a drive pulley that is 14 years old is not for the feint of heart. I struggled with the bolt for two days and 10 you tube videos later, success. Of course it was impossible without a pulley puller which I am very glad I purchased in advance. My impact wrench was useless unless I wanted to remove yet more "stuck" parts. I am satisfied with the performance and the annoying screeching of the alternator bearing is no more. I would recommend this product. Again; make sure you have the tools and patience as it is a must have during this project.

      MatthewW

      Year: 2003 Submodel: GT

      Helpful (0)

    • 4/5

      Installation Time: Full Day

      September 15, 2017

      Good product, the crank pulley is a tad tricky

      I've posted this same review on most other bolt-on products... It is well made and comes with what you need to install. I believe I put the brass spacer between the pulley and alternator. I bought all the typical bolt on stuff from SR Performance, (75 mm throttle body, plenum, spacer, CAI, UD Pulleys, etc...) and FRPP 4.10 gears. The car felt much better than stock! I recently took everything off for California SMOG, except the gears and hardly noticed any difference. I'm not going to bother reinstalling anything as I should have just listened to what EVERYONE else said and buy a blower... So I have a Kenne Bell ready to go on soon that IS California legal and will actually show massive gains. Not to knock SR Performance or any other company, but the bolt-ons just are not worth it. Save the money up for FI if you really want some power. AND DEFINITELY GET 3.73 OR 4.10 GEARS!!!

      Gezus

      Year: 2004 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      September 04, 2017

      Sr performance pulleys

      Fast shipping, good quality product, installation not to difficult, big performance improvement. Would strongly recommend these pulleys for that little bit of an edge in horse power gain.

      EdwardM

      Year: 2002 Submodel: GT

      Helpful (0)

    • 2/5

      Installation Time: Less than 1 Hour

      June 16, 2017

      shiny pulleys

      they are fine pulleys and look great but i wasn't happy with the piggy back style of the damper.

      sicsytec

      Year: 2003 Submodel: GT

      Helpful (0)

    • 5/5

      February 23, 2017

      Niiice

      They're pretty cool haven't found anyone to put them on yet. I'm glad I don't need a new belt.

      DESIII

      Year: 2000 Submodel: GT

      Helpful (1)

    • 5/5

      Installation Time: Less than 1 Hour

      February 18, 2017

      Awesome

      They installed easy look great added these and a kandn air intake and way more power and gas mileage

      KoryF

      Year: 2003 Submodel: GT

      Helpful (1)

    • 4/5

      Installation Time: Less than 1 Hour

      February 06, 2017

      Good product

      Nice look under the hood slight gains good bang for your buck

      JonathanP

      Year: 2003 Submodel: GT

      Helpful (1)

    • 3/5

      Installation Time: Afternoon

      January 17, 2017

      Bad01gt

      Good product very light a little fragile but got the job done in 1 hr notice a slight difference pay attention to the mid and late years choose the correct ones

      Bad01gt

      Year: 2001 Submodel: GT

      Helpful (1)

    • 5/5

      September 21, 2016

      Just what I needed.

      Look great. Smaller and Lighter then Factory Pulleys. My car just hit 176,000 miles and I recently paired these pulleys with some other engine repairs and my car is running great! Better than it ever has. Much more responsive, really pulls through every gear better and harder and gives a better exhaust note through every gear.. Also All that power that's taken when you turn on your AC is gone with these. Which is why I bought them. I am very satisfied.

      Dot

      Year: 2002 Submodel: GT

      Helpful (1)

    • 4/5

      July 12, 2016

      worth it

      Throttle response is quicker feel a noticeable power increase just suckes there piggyback

      02blackgt

      Year: 2002 Submodel: GT

      Helpful (2)

    • 4/5

      Installation Time: Afternoon

      April 22, 2016

      Great Replacement!

      These are a great Replacement for the OEM pulleys. I would recommend a friend help install them. And pay attention to the instructions!

      Levi

      Year: 2004 Submodel: GT

      Helpful (3)

    • 4/5

      Installation Time: Less than 1 Hour

      April 11, 2016

      Effective performance

      Solid product although I didn't like the piggie back pulley on the crank but all in all noticeable hp looks great and fairly simple to install I've owned probably 15 mustangs from fox bodies up and I have to say the 99 to 04's I've had a blast building more hp from these than any of the rest just by bolt on performance, thanks AM.

      Mustangnut

      Year: 2002 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $100-$250

      January 26, 2016

      Amazing product

      These under drive pulleys are a great product and for the price they can't be beat. My harmonic balancer was going out so these were just what i needed to fix the problem and add alittle horsepower as well as improve the look of my engine bay. I don't know exactly how much power was gained from them but i did notice the car was able to rev faster due to less parasitic loss from the engine components. Overall this is a very good product and i would buy it again.

      Thatguycody

      Year: 2003 Submodel: GT Birmingham, AL

      Helpful (2)

    • 4/5

      Installation Time: Shop Install

      Installation Cost: $100-$250

      October 05, 2015

      Great buy

      Very happy with these pulleys. Didn't take too long to instal and the gains were noticeable right away.

      Deeds

      Year: 2002 Submodel: GT Orlando, FL

      Helpful (2)

    • 4/5

      Installation Time: Less than 1 Hour

      August 05, 2013

      Good gain for the money!

      Installed in no time! You can feel the difference if you pay enough attention to your car, it's subtle but you can feel it.

      Coolgate

      Year: 2004 Submodel: GT Virginia

      Helpful (1)

    • 5/5

      Installation Time: Afternoon

      December 31, 2012

      Great Product!

      I bought these pulleys for my 04 gt, to start the instructions in the box were horrible! the kit comes with 2 brass washers and the instructions say nothing about the washers. for the alternator pulley the brass washer didn't even fit, good thing i work in a machine shop i had to Bore the washer out a good amount (.006") to get it to fit nice and snug. other then that putting them on went smooth. i felt a big difference over 3000 rpm's, you can feel the car throw you in your seat a lot more and i could most defiantly felt a difference. i had NO problems with my battery dying because of the alternator not charging. GREAT product i recommend 100%

      Yellow04gt

      Year: 2004 Submodel: GT

      Helpful (0)

    • 4/5

      Installation Time: Afternoon

      December 22, 2012

      2004 Mustang GT

      The pulleys are good quality. The performance improvement was very noticable in both throttle response and HP. The only problem is that the alternator pulley is a few hundredths too small for the factory alternator shaft. You need to be able to bore out the pulley slightly and evenly for installation.

      William64

      Year: 2004 Submodel: GT Tolland, CT

      Helpful (1)

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