Whiteline Rear Diff Positive Power Kit Inserts – 2008-2014 Subaru WRX / STI / 2009-2013 Forester / 2010-2013 Legacy

Whiteline Rear Diff Positive Power Kit Inserts – 2008-2014 Subaru WRX / STI / Forester

Insert-Based Rear Diff Mount Improvement for GR Subaru
The Whiteline KDT903 Rear Differential Positive Power Kit uses polyurethane inserts to fill the void space in the rear differential mount housings on the 2008-2014 Subaru WRX, STI, and Forester. The insert approach reduces differential movement without requiring full mount housing replacement, providing a meaningful compliance reduction with a simpler installation than the KDT906 full bushing replacement.

DETAILS

• Polyurethane inserts for rear differential mount positions on GR Subaru
• Reduces differential movement under acceleration and cornering
• Insert design — no OEM housing removal required
• Fitment: 2008-2014 Subaru WRX, STI, 2009-2013 Forester (GR chassis)
• Simpler installation than full bushing replacement

Insert vs. Full Bushing Replacement
The KDT903 uses inserts that fill the void in the existing OEM mount housing — a simpler approach than the KDT906 which replaces the full bushing. For mounts that are in acceptable condition with normal void space wear, inserts produce most of the compliance reduction benefit with less installation complexity.

GR Chassis Coverage
One insert kit covers the GR WRX, STI, and SH Forester — three models that share compatible rear differential mount geometry on the GR chassis platform.

Part of the GR Drivetrain Package
The rear diff inserts work alongside front differential mount inserts (KDT905) and transmission mount inserts (KDT956) for a complete GR drivetrain mount improvement package.

Why Choose Whiteline

Whiteline has been engineering suspension components from their facility in Australia since 1979. Every product in their catalog is developed with a clear goal: measurable improvement in handling, stability, and tyre contact. Whiteline’s polyurethane bushings, sway bars, control arms, and alignment correction kits are engineered using finite element analysis and validated on track before they reach the market. Their components are direct-fit, bolt-on solutions designed for enthusiasts who want real performance gains without fabrication or custom work.

The RallySport Take

Effective and easy-to-install rear differential mount improvement for the GR Subaru platform. The install is straightforward but doing it correctly matters — clean the housing thoroughly before installation and apply grease to all polyurethane-to-metal contact surfaces. The improvement in drivetrain feel shows up immediately on the first hard acceleration run after installation.

What’s in the Box

• Polyurethane inserts for rear differential mount positions on GR Subaru
• Reduces differential movement under acceleration and cornering
• Insert design — no OEM housing removal required

Fitment