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SR Performance Underdrive Pulleys; Black (Late 01-04 Mustang GT)

Item 525575
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      Video Review & Installation

      Hey, guys. Stephanie with, here with a review of SR Performance underdrive pulleys for late 2001 to 2004 GT Mustangs. You're going to want to check out the SR Performance underdrive pulleys if you're looking to free up a touch of horsepower in a fast, easy, and very affordable way. The SR Performance costs the least out of any pulley option, and the theory behind underdrive pulleys is that the factory pulleys require a lot of energy. Instead of lightweight aluminum pulleys like these here, reduce the amount of parasitic drivetrain loss, by cutting down on the amount of power that it takes to run the accessories, like the water pump, alternator, and AC compressor. Some people mention noticing a difference after installing these underdrive pulleys. Underdrive pulleys are only a good idea if you plan on keeping your car NA. So just keep that in mind when you're figuring on your future plans. The install for these is going to be an easy one out of three wrenches on the difficulty meter, and you can plan on spending two hours to get the job done. So the engine uses its own power to rotate the serpentine belt, starting at the crankshaft. This pulley then uses the engine's power to rotate the rest of the pulley. So when you reduce the size of the crankshaft pulley, it'll require less energy to rotate the accessories. The pulleys on this side are lightweight aluminum, which means that they'll require even less energy to rotate. This set is powder-coated black, but SR Performance also sells a polished set too, if you prefer the look of those instead. The polished pulleys will cost about $20 more, though. So just keep that in mind. This kit is going to include the crank pulley, the water pump pulley, and the alternator pulley, as well as the hardware to get these installed. The nice thing about these, they're going to free up the power that the engine is currently using to rotate these pulleys, but you won't sacrifice the effectiveness of the accessories. So your water pump and your alternator will still function perfectly. They'll just require less power from the engine to operate. The only time you can see issues is if you have an aftermarket sound system and upgraded alternator. These items are more taxing on the car system, and require more work from the alternator. So if that's the case, I'd recommend steering away from underdrive pulleys. But for those of you that don't have that setup, these will reuse the stock belt. So you won't have to get a different-sized belt, which will make it easier when you need to replace your belt down the road. When it comes to fitment, adjust to make sure you're shopping for the correct year range here. This kit is for the late '01 to '04 GTs with the short water pump. Halfway through '01, Ford changed some things in production. So if you have an early '01 model, you need to pick up the other pulley set. The older water pump style, up until mid-'01, had a longer shaft, and will need a different water pump pulley because of this. As far as price, you're looking at a touch over $100 for this kit. It's the most affordable pulley kit currently at this time. Don't forget, you do have the choice of the SR Performance polished pulley kit if you didn't want the black set, or you have the choice of another brand, like BBK or Steeda. The install here is easy, and I'm going to call it a one out of three wrenches on the difficulty meter. You can expect to spend about two hours getting the install done, and you just need some basic hand tools to get the job done. You need to release the tension on your serpentine belt and set it aside. From there, it's a matter of unbolting the factory pulleys and replacing them with the underdrive pulleys from SR Performance. Once they're bolted on, release the tension pulley again and put the serpentine belt back on. You need to make sure it's on properly, following the diagram usually located on the rad cover. Wrapping things up here with the SR Performance underdrive pulleys, these pulleys are for the late '01 to 2004 Mustang GT, and you can check them out more online right here at

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation

      Features & Specs

      • Free Up 10-15 Horsepower
      • Complete 3 Piece Kit
      • Durable, Lightweight Aluminum
      • Black Powder Coated Finish
      • Premium Quality Construction
      • Fits Late 2001-2004 GT Mustangs


      Free Up Horsepower. A set of SR Performance Underdrive Pulleys reduce parasitic drivetrain loss by cutting down the amount of power your accessories take up, these underdrive pulleys will free up 10-15 horsepower, without sacrificing cooling and charging functionality of your Pony.

      Premium Quality Construction. CNC-machined from lightweight aircraft grade quality aluminum alloy for strength and durability, these SR Performance pulleys feature a gloss black powder coated finish for aggressive good looks and long lasting corrosion resistance.

      Easy Installation. These SR Performance Mustang Underdrive Pulleys installs quickly and easily in under 2 hours with no modifications required.

      Application. This SR Performance 3-Piece Aluminum Underdrive Pulley Kit is designed for use on Late 2001 to 2004 GT Mustangs equipped with the SOHC 4.6L V8 engine and the a short water pump (bowed in face). Reuses factory 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.

      SR Performance



      SR Performance 525575

      CA Residents: WARNING: Cancer and Reproductive Harm -

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) Crank Pully
      • (1) Water Pump Pully
      • (1) Alternator Pully
      • (4) Bolts
      • (3) Washers
      • (2) Spacers
      • (1) Instruction Sheet


      Customer Reviews (494)

        Questions & Answers

        10 More Questions

        Will It Fit My Mustang

        • GT - 01, 02, 03, 04

        Fits GT Mustangs with the short water pump with a bowed in pulley.

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