GReddy Underdrive Pulley Kit – Toyota 2JZ / 1JZ | JZX100 (Mark II / Chaser / Cresta) / JZZ30 (Soarer)

The GReddy Underdrive Pulley Kit for the Toyota 2JZ and 1JZ engines in the JZX100 and JZZ30 chassis is an underdrive accessory drive pulley kit engineered to reduce the parasitic power loss caused by the factory accessory drive system — freeing up horsepower and torque that would otherwise be consumed driving the alternator, power steering pump, and other accessories at the factory pulley ratio. By using larger diameter pulleys than the factory units, the GReddy kit reduces the rotational speed of the accessory drive components relative to the crankshaft — reducing the load on the engine and recovering power at the crank. GReddy (Trust) is one of the most iconic and respected JDM performance brands in the world — a Japanese manufacturer with decades of motorsport and performance development experience for Toyota, Nissan, and other Japanese performance platforms.

Key Features:

• Underdrive pulley design — larger diameter pulleys than the factory units reduce the rotational speed of the accessory drive components relative to the crankshaft — reducing the parasitic load on the engine and recovering power that would otherwise be consumed by the accessory drive
• Reduces parasitic power loss — the factory accessory drive system consumes a meaningful amount of crankshaft power driving the alternator, power steering pump, and other accessories at factory speed — underdrive pulleys reduce this parasitic load for improved power delivery at the wheels
• Lightweight construction — GReddy's pulley kit uses lightweight materials compared to the factory cast iron or steel pulleys — reduced rotating mass for improved throttle response and engine rev characteristics
• 2JZ and 1JZ compatible — correct for both the 2JZ (2JZ-GE and 2JZ-GTE) and 1JZ (1JZ-GE and 1JZ-GTE) engines in the JZX100 and JZZ30 chassis
• JZX100 and JZZ30 applications — correct for the Toyota Mark II, Chaser, and Cresta (JZX100) and the Toyota Soarer (JZZ30)
• GReddy quality — manufactured by GReddy (Trust), one of the most iconic and respected JDM performance brands in the world

Underdrive Pulleys — How They Work:

The factory accessory drive system uses a belt driven by the crankshaft pulley to spin the alternator, power steering pump, air conditioning compressor, and other accessories. The ratio between the crankshaft pulley diameter and the accessory pulley diameters determines how fast each accessory spins relative to the engine. Underdrive pulleys use a larger crankshaft pulley and/or smaller accessory pulleys to reduce the accessory drive ratio — spinning the accessories more slowly relative to the crankshaft. This reduces the torque required to drive the accessories, reducing the parasitic load on the engine and freeing up power at the crank. The power recovery from underdrive pulleys is most noticeable at higher RPM where accessory drive loads are greatest. On a modified 2JZ or 1JZ build where every horsepower counts, underdrive pulleys are a meaningful and cost-effective power recovery modification.

2JZ / 1JZ — Platform Context:

The Toyota 2JZ and 1JZ inline-six engines are among the most celebrated and widely modified Japanese performance engines ever produced. The 2JZ-GTE in particular — as used in the Toyota Supra (JZA80) and available as a swap option for the JZX100 and JZZ30 — is renowned for its exceptional strength and power potential. The 1JZ-GTE is equally respected in the JDM performance community for its compact dimensions and strong power potential in the JZX100 and JZZ30 chassis. For 2JZ and 1JZ builds where maximum power extraction is the goal, the GReddy underdrive pulley kit is a proven and respected modification from one of the most trusted names in JDM performance.

Specifications:

• Brand: GReddy (Trust)
• Part Number: GRE13512110
• Type: Underdrive pulley kit
• Engine Compatibility: Toyota 2JZ (2JZ-GE / 2JZ-GTE) / 1JZ (1JZ-GE / 1JZ-GTE)
• Application: JZX100 (Toyota Mark II / Chaser / Cresta) / JZZ30 (Toyota Soarer)
• Weight: 1.8 lbs (kit weight)

Fitment Information:

• Toyota JZX100 — Mark II / Chaser / Cresta — 1JZ-GE / 1JZ-GTE / 2JZ-GE
• Toyota JZZ30 — Soarer — 1JZ-GTE / 2JZ-GE
• Note: Verify your specific JZX100 or JZZ30 engine variant before ordering — confirm that GRE13512110 is the correct pulley kit for your specific 2JZ or 1JZ configuration. Underdrive pulleys may affect alternator output at idle and low RPM — verify electrical system compatibility, particularly on builds with high electrical loads (large audio systems, additional lighting, etc.). Air conditioning performance may be reduced with underdrive pulleys installed. Professional installation recommended.

What's Included:

• GReddy underdrive pulley kit — Toyota 2JZ/1JZ JZX100/JZZ30 (GRE13512110)
• Refer to GReddy's product documentation for complete kit contents and pulley specifications

Installation Notes:

• Professional installation recommended — pulley replacement requires correct torque at the crankshaft bolt and correct belt tension after installation
• Use a crankshaft holding tool to prevent the engine from rotating during crankshaft pulley bolt removal and installation — do not use the starter motor to hold the engine
• Torque the crankshaft pulley bolt to the correct specification — refer to GReddy's installation documentation for correct torque values
• Verify correct belt tension after installation — incorrect belt tension will cause belt slip, premature belt wear, and accessory drive failure
• Check alternator output voltage at idle after installation — underdrive pulleys reduce alternator speed at idle and may reduce charging voltage — verify that the battery charges correctly at idle with the underdrive pulleys installed
• Air conditioning performance may be reduced — the reduced compressor speed from underdrive pulleys may affect air conditioning cooling capacity, particularly at idle

Why GReddy?

GReddy (Trust) is one of the most iconic and respected JDM performance brands in the world — a Japanese manufacturer with decades of motorsport and performance development experience for Toyota, Nissan, and other Japanese performance platforms. GReddy's product lineup spans turbochargers, exhaust systems, intercoolers, engine management, and performance accessories — all developed with the same commitment to JDM performance engineering that has made GReddy a trusted name in the global JDM community. For 2JZ and 1JZ owners who want a quality underdrive pulley kit from one of the most respected names in JDM performance, GRE13512110 is the correct choice.

Perfect For:

• Toyota JZX100 (Mark II/Chaser/Cresta) and JZZ30 (Soarer) owners with 2JZ or 1JZ engines who want to reduce parasitic accessory drive losses and recover power at the crank with GReddy's underdrive pulley kit
• Modified 2JZ and 1JZ builds where every horsepower counts and underdrive pulleys are a cost-effective power recovery modification from a trusted JDM performance brand
• JZX100 and JZZ30 performance builds where reduced rotating mass from lightweight underdrive pulleys improves throttle response and engine rev characteristics alongside the power recovery benefit

Note: Verify alternator output at idle after installation — underdrive pulleys reduce alternator speed. Air conditioning performance may be reduced. Verify JZX100/JZZ30 engine variant before ordering. Use crankshaft holding tool during installation. Torque to GReddy's specification. Verify correct belt tension after installation. Professional installation recommended.