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BBK Underdrive Pulleys (Late 01-04 GT)

Market Price $183.99 You Save 13% ($24.00)
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  • Item 56008
  • MPN# 1559

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Features & Details

  • Gain Up to 15HP
  • Three Piece Kit
  • Brilliantly Polished Finish
  • Fits Late 2001 to 2004 GT
Gain 15HP. Improve throttle response and add power throughout your RPM range by reducing the amount of power you're losing to your accessories. And best of all, you don't have to sacrifice your A/C or charging performance - you can free up as much as 15HP with a set of BBK underdrive pulleys for your GT without negatively affecting your Mustang's ability to keep you cool.

Premium Quality. Made of aircraft quality aluminum alloy, these BBK aluminum pulleys won't weigh you down.

Hand Polished. The brilliant polished finish of these underdrive pulleys will give your engine bay a high performance look.

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

Application. These BBK underdrive pullies are designed to fit the Late 2001 to 2004 GT Mustangs 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) Water pump pulley
  • (1) Alternator pulley
  • (1) Crank pulley
Installation Info
Tech Specs
UnderDrive Pulley Specifications
Year/Model: Late 2001-2004 GT Manufacturer: BBK
Material: Aluminum Finish: Polished
Crank Pulley: Piggyback SFI Certified: No
Will it fit my Mustang?
  • GT - 01, 02, 03, 04

Fits Mid 2001 to 2004 GT's Only

People Who Bought This Item Also Bought

Most Helpful Reviews

Why didn't I do this sooner

Love the pully's!! Cheep in price and noticable power all the way through the RPM band. Only problem is the 3 speeding tickets I got in the last month.

Helpful (24)


Straight forward, easy install, well once you get the stock parts off. Only thing me n my buddy had trouble with was getting the stock harmonic balancer off but once we got it off, the rest was cake. Nice ...

Read More
Helpful (19)

Overall Rating 4.6 out of 5 stars
Read All 38 Reviews

Customer Photos (12) Submit Your Photo

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9 Questions / 6 Answers

Ask a Question

Will the stock size belt work?


  • These BBK Underdrive Pulleys do not require an aftermarket belt size and will work with the factory belt size.


Helpful (0)

how would these pulleys affect boost from procharger


  • We do not recommend using the BBK Underdrive Pulleys, or any other underdrive pulleys on a supercharged setup, as this will reduce boost, causing a loss in horsepower and torque, as the supercharger kits are designed around stock pulley diameters.

    Rob D

Helpful (0)

I bought these from a app and it didn't come with some of the bolts and rings and washers where could I get replacement set without buying a whole new pulley set?


  • Unfortunately, we only sell the full set. I would recommend contacting BBK directly.


Helpful (0)

Will this work with a 2004 Mustang V6?


  • These BBK Underdrive Pulleys are designed specifically for the GT, and would not fit the V6.

    Rob D

Helpful (0)

What is the difference from the bbk pulleys and the sr peformance ?


  • The only real difference between the BBK and the SR Performance underdrive pulleys is their appearance. They are the same size, built of similar metals and have the same functions. The BBK is a polished finish whereas the SR Performance is of a black finish.


Helpful (0)

Does these fit on 03 mach 1???


  • No, this fits mid 2001 to 2004 GT's only.


Helpful (0)

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Customer Reviews (38) Write a Review

Overall Rating 4.6

out of 5 stars

Installation Time:Afternoon

Installation Cost:$100-$250

  • Performance Gain 4.529412 4.5
  • Fit 4.941176 4.9

  • 5/5

    June 23, 2010

    Why didn't I do this sooner

    Love the pully's!! Cheep in price and noticable power all the way through the RPM band. Only problem is the 3 speeding tickets I got in the last month.

    J. White

    Helpful (24)

  • 5/5

    July 11, 2010

    BBK UDPs

    Straight forward, easy install, well once you get the stock parts off. Only thing me n my buddy had trouble with was getting the stock harmonic balancer off but once we got it off, the rest was cake. Nice increase in throttle response, my car was noticeably quicker. To the previous reviewer, maybe if you got the right pullies for your year, you wouldn't have had those problems.


    Helpful (19)

  • 5/5

    April 13, 2009

    03 GT

    I added these pulleys and got 12 more horses. Quick and easy hps. Takes 30 minutes tops.


    Year: 2003 Submodel: GT

    Helpful (9)

  • 4/5

    October 20, 2010

    BBK Underdrive pulleys

    Install was very easy overall. Once I got them on and drove my car i was super impressed at how fast my car picked up when floored. My only gripe is that this is a piggy back setup. If i would have known that I would have bought the Steeda kit instead. Great though if your trying to get the performance and save a few bucks.

    Matt W.

    Helpful (8)

  • 5/5

    June 30, 2010

    2005 4.6 single valve motor

    This underdrive pulley kit works great. However, the water pump pulley wears out quick. It only had 18000 miles.The Serpentine belt wears a deep groove in the water pump pulley and it results in the belt tensioner meeting with the belt and ul;timately a belt failure. I wont buy again. I put the factory belt pulleys back on. Considering the cost of the product, longevity should have been way longer. Not worth the buy.


    Year: 2005

    Helpful (6)

  • 5/5

    October 06, 2009

    Worth the price

    Installed on my 01 GT. I put these on after I sold vortech blower and set car up to run nitrous, best thing I ever did, I did a few thousand bucks worth of mods at once so Im not sure if Id notice the power ofem but they look good. O and dont be dumb REUSE UR DAMPER! Just paint it black and bolt it onto the face of the bbk crank pulley like its suppose to be. I see so many people not doing this, Not the smartest thing in my book..


    Year: 2001 Submodel: GT

    Helpful (6)

  • 4/5

    Installation Time: Shop Install

    Installation Cost: $100-$250

    September 19, 2012

    good product

    It helped my gas mileage a bit and i needed that little extra power to get my stang to 350 hp. AM has never disappointed me and I still purchase products nonstop. Stop reading reviews and just buy it fool!


    Year: 2003 Submodel: GT michigan

    Helpful (5)

  • 4/5

    August 18, 2010

    nice addition

    a fairly simple install, my advice is to get a proper harmonic balancer puller and remove the fan to give you some additional room to work. throttle response was crisper, and no noticeable affect on cooling. great product at a decent price. looks nice under the hood when all polished up


    Helpful (5)

  • 5/5

    Installation Time: Afternoon

    November 11, 2012

    Excellent with a fresh air intake.

    We went on a road trip to Boston. The trip was just over 3800m. I averaged 20.3 mpg. This year we went on a roadtrip to Yellowstone, about 5300m. I averaged 23.04 mpg. The changes in the car between the trips where a fresh air intake, under drive pulleys, and a 3 tune chip. The tune made the least impact in fuel economy. I used the street tune for the trip out on I94 and the stock tune on the I90 heading home. They came back as 24.52 and 24.14 repectively. The flat highway average for the whole trip is 24.35. Not too much difference but it is there. The intake and pulleys took the mileage up over 13%. I think that is pretty impressive. The car is a ragtop. The coupe will do better. On the performance end of things the results are the same. There is a huge difference in driveability. Both the intake and the pulleys changed the way the car performs coming off the line. They made the car feel lighter and stronger. The difference with the chip is there but shows up more on the track performance with the performance 87 and race 91 tunes. The intake and pulleys are must haves, the chip is a nice to have.


    Year: 2004 Submodel: GT Ottawa, Ontario, Canada

    Helpful (3)

  • 5/5

    Installation Time: Afternoon

    May 13, 2014

    Money well spent

    I attempted this project myself, I'm not a tech, but I am a service advisor at a local chain repair shop so I had help when I needed it. The alternator and water pump pulley came off no problem, with the crank pulley I had a little help from a tech. All 3 pulleys fit perfectly and look awesome under the hood. Total time for install was about 2 hours. Engine seems to rev up quicker, can't wait to get down to the drag strip. Thanks to AM for awesome website!! Easy to navigate and full of information.


    Year: 2002 Submodel: GT London, ON, Canada

    Helpful (2)

  • 5/5

    May 19, 2008

    BBK Underdrive Pulleys for my 2002 GT

    My mechanic just installed these and I can notice a good gain through out the entire power band. The only problem we ran into is that some 2002 GTs will actually have the water pump from 2001. Not a huge problem just change the water pump to fit. Other than that nice product.

    Joe Flemming

    Year: 2002 Submodel: GT

    Helpful (2)

  • 5/5

    August 16, 2016

    Great product

    Love the pulleys I can blow my air and not lose any power


    Year: 2004 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Shop Install

    July 21, 2015

    They look awesome

    I had these pulleys installed, at the same time, with a few other mods. I actually went to my local Ford dealer; nothing beats a professional job and they stand behind their work 100....(added bonus I got to test drive the 2015 GT, with performance package:) ). they look great, I can definitely feel more power and much better throttle response, especially over 3000 rpms but..... it might just be the 410 gears I also added at the same time....


    Year: 2003 Submodel: GT Montreal

    Helpful (1)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: $100-$250

    March 16, 2014

    great response

    I really noticed the throttle response and pretty descent acceleration. Looks awsome, worth the price.


    Year: 2003 Submodel: GT Memphis, TN, USA

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    February 15, 2014

    be prepared

    I got these pulleys because i already had to replace my belt tensioner and idler pulley, so figured i might as well do an upgrade while I'm at it. and for a fairly inexperienced car guy the install was pretty straight forward, when taking off the stock crank pulley you WILL NEED A PULLEY PULLER, AND A BIG BREAKER BAR. took a lot more force to get the bolt out than i had anticipated, great product though! may have gone with the steeda kit if i had realized it was a piggy back style kit, but none the less this will work perfectly on your car, i am 100% satisfied


    Year: 2004 Submodel: GT Dallas, TX

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    September 28, 2013

    great product!

    I ordered these pulleys from AM on a monday and got them on a wednesday. the only hard part of the installation was getting the old pulleys off. Other than that its good to go and I noticed a good gain in tq and hp. I would highly recommend this product to anybody


    Year: 2003 Submodel: GT

    Helpful (1)

  • 5/5

    March 08, 2010

    bbk pullies

    Look great i can feel better throttle response

    Matt m

    Helpful (1)

  • 5/5

    July 16, 2009

    Underdrive Pulley Kit (01-04 GT) Review

    These pulleys were very easy to install, and the performance was noticeable especially when the air-conditioning was turned on. I am very happen with this product and would recomend it to others

    Tom Hertzog

    Helpful (1)

  • 5/5

    October 22, 2008

    Very nice

    Got these a month ago for my 01 GT and was very impressed for price. Well made and a nice finish. Set these next to your stock pulleys and the difference in weight is amazing. Noticeable performance gain in response and between gears. ONLY TOOK ME 45 MINUTES TO INSTALL. Great to work with! Fast shipping, low price, and great product.


    Year: 2001 Submodel: GT

    Helpful (1)

  • 2/5

    Installation Time: Afternoon

    October 31, 2017


    Terrible product! Install directions TERRIBLE! The piggy back set up is just ridiculous anyways! It looks ridiculous also! Gave me check engine light for random misfires. Returned the stock the light went off.


    Year: 2004 Submodel: GT

    Helpful (0)

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