Part Number:

• KB-003-Diff-H (Race)

• KB-003-Diff-S (Soft)

Description: Kartboy Rear Differential Outrigger Bushings

Fitment: 02-07 Subaru WRX & STI

Available: Standard & Soft Bushings

Details:

Eliminate Rear Differential Clunk Without Compromising Cabin Comfort
Tired of hearing that loud, annoying "clunk" from the rear end during fast gear changes or aggressive launches, but don't want the harsh noise and vibration of a solid race setup? The Kartboy Rear Differential Outrigger Bushings - Soft/Comfort Version (KB-003-Diff-S) eliminate rear differential slop while keeping cabin NVH (noise, vibration, and harshness) at a comfortable daily-driver level.

Soft Comfort-Formulated Polyurethane for Smooth Daily Driving
Molded from a specially formulated street-spec polyurethane, these insert bushings sandwich your vehicle's factory outrigger mounts to fill the massive air gaps in the OEM rubber. By stabilizing the rear diff without locking it down rock-solid, you get sharper throttle response and cleaner gear shifts while maintaining factory-like ride comfort.

Race 95A Durometer Polyurethane for Maximum Power Transfer
Molded from high-durometer (95A) race-spec polyurethane, these insert bushings sandwich the factory outrigger mounts to lock down differential movement. By preventing the rear diff from twisting and winding up under acceleration, engine torque is delivered directly to the ground for sharper throttle response, instantaneous gear engagement, and reduced wheel hop.

Soft Key Features:

• Reduces Rear Diff Clunk: Prevents the differential outrigger arm from slamming into the subframe under acceleration.

• Daily-Driver Comfort Spec: Softer polyurethane formulation minimizes cabin NVH while drastically reducing driveline slop.

• Improved Throttle Response: Eliminates driveline wind-up for faster power transfer to the wheels.

• Simple Sandwich Install: Drops in around factory rubber bushings without requiring press tools or subframe removal.

• Made in USA: Designed, molded, and packaged in the USA by Kartboy.

Race Key Features:

• Eliminates Diff Clunk: Prevents the rear differential outrigger arm from slamming into the subframe under hard acceleration or fast shifts.

• 95A Hard Durometer (Race Spec): Ultra-stiff polyurethane formulation engineered for maximum power transfer and minimal flex.

• Improved Throttle Response: Eliminates driveline "wind-up" for immediate power delivery to the rear wheels.

• Direct Sandwich Installation: Installs easily around the factory rubber bushings without requiring expensive hydraulic press tools.

• Made in USA: Formulated, poured, and tested in the USA by Kartboy.