Upgrading the pulley on your Jeep Grand Cherokee Trackhawk is one of the most popular and cost-effective modifications for unlocking extra horsepower and torque from the supercharged 6.2L Hemi Hellcat engine. By reducing the pulley diameter, you spin the supercharger faster, increasing boost pressure and forcing more air into the engine. However, a successful upgrade requires careful planning, the right tools, and attention to detail. This expanded guide walks you through every step, from understanding the pulley system to post-installation tuning, ensuring you get reliable gains without damaging your engine.

Understanding the Trackhawk Pulley System

The Trackhawk uses a positive-displacement supercharger (an IHI twin-screw unit) driven by a serpentine belt connected to the crankshaft. The factory pulley sits at approximately 2.72 inches in diameter. Switching to a smaller pulley — typically 2.62 or 2.53 inches — increases supercharger impeller speed by roughly 5–10%, producing 2–3 psi more boost. This translates to gains of 30–60 wheel horsepower and 40–70 lb-ft of torque on an otherwise stock engine, depending on fuel quality and supporting modifications.

Before diving in, understand that pulley upgrades push the engine beyond factory calibration limits. The stock fuel system, injectors, and spark timing are not optimized for higher boost. Adding a smaller pulley without tuning can lead to detonation, high exhaust gas temperatures, and potential engine damage. A custom tune via an ECU flash or handheld programmer is essential to adjust air/fuel ratios, ignition timing, and other parameters. Many owners combine a pulley upgrade with a cold air intake, larger heat exchanger, and cat-back exhaust to maximize gains and keep intake air temperatures in check.

Tools and Materials Needed

Having the correct tools on hand before you begin saves time and prevents frustration. Below is a comprehensive list, including both essential and highly recommended items.

  • Socket set – SAE and metric, including a 15mm socket for belt tensioner and 18mm for crank bolt (though crank pulley is not removed).
  • Torque wrench – Ensure it's calibrated; you'll need it for supercharger pulley bolts (typically 18–22 ft-lbs with loctite).
  • Pulley puller/separator tool – A dedicated supercharger pulley puller (e.g., ZPE, RIPP, or a generic harmonic balancer puller kit) that fits the splined shaft of the IHI blower.
  • Replacement pulley – Choose from reputable manufacturers like Hennessey, 1320 Junkie, or RIPP Superchargers. Ensure it matches your desired boost level and belt size.
  • Loctite thread locker – Blue (242) is standard for pulley bolts; avoid red unless specified as it's permanent.
  • Serpentine belt (if needed) – Smaller pulleys often require a slightly shorter belt (e.g., Gates K070565 or equivalent). Verify belt size with your pulley vendor.
  • Belt tensioner tool – A 15mm socket on a long breaker bar works, but a dedicated serpentine belt tool makes the job easier.
  • Torx bits (T25, T30) – For removing plastic engine covers and brackets.
  • Rags and degreaser – Clean the supercharger snout area before removal to prevent debris from entering the intake.
  • Safety gloves and goggles – Pulley installation involves spring tension and metal parts; protect yourself.
  • Optional but recommended: DiabloSport i3 or i2030 tuner for post-install tuning, a belt tension gauge (Krikit type), and a mirror on a stick to inspect belt routing.

Step-by-Step Installation Process

Perform this installation on a cold engine in a well-ventilated area. Disconnect the negative battery terminal first and wait 10 minutes for the electrical system to fully discharge. This prevents accidental airbag deployment or sensor damage.

Step 1: Remove Engine Cover and Access Belt

Unclip the plastic engine beauty cover by pulling upward. Disconnect any vacuum lines or wire harness clips attached to the cover. With the cover removed, locate the serpentine belt and the belt tensioner near the top front of the engine (passenger side). Using a 15mm socket on a breaker bar, rotate the tensioner counterclockwise to relieve belt tension. Slip the belt off the supercharger pulley first, then off the other pulleys. Inspect the belt for cracks or glazing; replace if worn.

Step 2: Access the Supercharger Pulley

You may need to remove the air intake tube and the throttle body inlet elbow for clearance. On Trackhawks, the intake tube is held by a worm gear clamp (7mm socket) and a 10mm bolt near the throttle body. Gently pull the tube off the throttle body and move it aside. The supercharger pulley is now visible on the driver side, directly behind the alternator. If needed, unbolt the alternator (two 13mm bolts) and move it slightly outward — do not disconnect the electrical connector; just tilt it for access.

Step 3: Remove the Factory Pulley

Center the puller tool on the supercharger shaft's retaining bolt (usually a Torx T40 or an 8mm hex). Apply the puller's forcing screw against the center bolt while the legs grip the pulley hub. Do not use an impact gun on the center bolt — you risk stripping the supercharger snout threads. Slowly tighten the puller until the pulley pops off the splined shaft. It may require significant force; a sharp pop is normal. Once removed, clean the shaft with a lint-free rag and inspect for any burrs. Deburr gently with fine emery cloth if necessary.

Step 4: Install the New Pulley

Apply a thin layer of anti-seize or a few drops of oil to the splined shaft for easier installation. Slide the new pulley onto the shaft by hand as far as it will go. Using the same puller tool (but reversed as an installer), press the pulley fully onto the shaft. Ensure it is seated flush against the supercharger bearing race — no gap. Some aftermarket pulleys come with a set screw; do not over-tighten it as it can distort the pulley. Apply blue Loctite to the pulley retaining bolts (if any) and torque to the manufacturer's specification, typically 18–22 ft-lbs.

Step 5: Replace the Serpentine Belt and Reassemble

Refer to the belt routing diagram on the fan shroud or look up the correct path for your new pulley diameter. A smaller pulley often requires a belt that is 1–2 inches shorter. Use the belt specified by your pulley vendor. Route the belt over all pulleys except the tensioner, then rotate the tensioner with the 15mm socket and slide the belt onto the supercharger pulley last. Release tension slowly. Check that the belt is fully seated in all grooves. Reinstall the alternator (if moved), intake tube, and all brackets. Reconnect any sensors or vacuum lines. Double-check that no tools or rags are left in the engine bay.

Step 6: Reconnect Battery and Initial Start

Reconnect the negative terminal. Turn the key to ON position (without starting) and wait for the fuel pump to prime. Start the engine. Do not rev the engine immediately. Let it idle for 30 seconds while you listen for belt squeal, unusual chirps, or rubbing sounds. If the belt squeals, check tension and alignment — a misaligned pulley can cause premature belt failure. Allow the engine to reach operating temperature and verify coolant fan operation. Shut off, let cool, then re-torque the pulley bolts one final time.

Tuning and Calibration Considerations

As emphasized, a pulley upgrade requires recalibrating the Engine Control Module (ECM). Running higher boost on the stock tune can exceed the knock sensor's ability to compensate, leading to engine damage. You have two primary tuning paths:

  • Handheld tuner with preloaded tunes – Devices like the DiabloSport i3 or HP Tuners' RTD allow you to flash a tune matched to your pulley size, fuel octane (91 or 93), and modifications. Many vendors (e.g., HemiTuner) offer custom files via email after you data-log the first start.
  • Dyno tuning – For maximum power and safety, a professional dyno tune adjusts air/fuel ratio, timing, transmission shift points, and torque management. Expect to pay $600–$1,000 but get a precise calibration.

Regardless of the method, you'll need to log parameters like boost pressure, fuel trims, knock retard, and intake air temperature. Never ignore a persistent knock count or high exhaust temps. Upgrading the low-pressure fuel pump (Fore Innovations or similar) may be necessary if your boost level exceeds 12–13 psi and fuel pressure drops.

Common Issues and Troubleshooting

Even with careful installation, problems can arise. Here are the most frequent ones and how to resolve them.

  • Belt squeal on startup – Usually caused by insufficient tension or a belt that's too long. Verify the belt size using the manufacturer's recommendation. A tension gauge should read 120–140 lbs on a cold engine.
  • Pulley wobble – Indicates the pulley is not fully seated on the spline. Remove and reinstall, ensuring it's pressed flush. Check the supercharger shaft for damage.
  • Check engine light (P0128 or P0172) – Coolant temp below thermostat regulating temp (P0128) or rich fuel trim (P0172) often means the tune needs adjustment. Contact your tuner.
  • Boost spike or overboost – The supercharger bypass valve may not be controlling pressure correctly. Verify the bypass valve solenoid and vacuum lines. A larger pulley may actually be needed if boost exceeds 15 psi on pump gas.
  • Knock sensor activity – If you hear pinging under load, stop driving immediately. Lower the boost via a smaller pulley or upgrade fuel octane (e.g., mix in E85 if your tune supports flex fuel).

If you're unsure about any symptom, consult a reputable performance shop that specializes in Hellcat platforms. Forums like Hellcatforum.com and Trackhawkforum.com are invaluable resources for troubleshooting specific codes.

Performance Gains and What to Expect

A properly installed pulley upgrade with a tune will deliver noticeable seat-of-the-pants improvement. On a 93-octane tune, a 2.62-inch pulley typically yields 550–570 wheel horsepower and 570–590 lb-ft, up from stock ~520 whp. A 2.53-inch pulley with supporting mods (cold air, ported snout, lower pulley) can push 600+ whp. Quarter-mile times drop from 11.6–11.8 seconds stock to the low 11s or even high 10s with proper traction.

To realize these gains reliably, consider these complementary upgrades:

  • Cold air intake – Reduces inlet restriction and lowers IATs.
  • Heat exchanger (HE) – A larger or dual-pass HE improves intercooler efficiency, critical for sustained boost in hot weather.
  • 1100cc injectors & upgraded fuel pump – Necessary for any pulley below 2.62 or if running E85.
  • Wider drag radials – Tire spin becomes a major limiting factor; 305/35R20 Nitto NT05R or Mickey Thompson ET Street SS are popular.

Remember that every vehicle behaves differently — altitude, fuel quality, and ambient temperature all affect results. Data-log after your first few pulls and watch for any signs of knock or excessive fuel trims.

Conclusion

Installing a smaller supercharger pulley on your Trackhawk is a rewarding project that can transform your truck's acceleration and overall performance. By following this step-by-step guide, using quality tools, and pairing the upgrade with a proper tune, you'll unlock the Hellcat engine's potential without sacrificing reliability. Always prioritize safety — if you lack mechanical experience or access to a dyno, enlist a professional installer and tuner. With careful attention to detail, your Trackhawk will reward you with a blistering driving experience every time you press the throttle.