COBB Rear Differential Subframe Mount Bushing Insert – 2008-2021 Subaru WRX/ STI

Cobb Rear Differential Subframe Mount Bushing Insert — 2008-2021 Subaru WRX / STI

The Cobb bushing kit for 2008-2021 Subaru WRX replaces the factory rubber rear differential subframe mount bushing inserts with polyurethane units. Addresses drivetrain movement at this specific mount location — improving drivetrain rigidity and reducing the compliance that allows the differential or transmission to shift under load.

DETAILS

• Platform: 2008-2021 Subaru WRX, 2008-2021 Subaru WRX STI
• Replaces: rear differential subframe mount bushing inserts
• Polyurethane — tighter durometer than factory rubber
• Reduces drivetrain movement at this specific mount location
• Standalone for targeted replacement or as part of complete driveline bushing upgrade

Rear Differential Subframe Mount Bushing Inserts: Targeted Drivetrain Compliance Reduction

Suspension and drivetrain bushings are the rubber or polyurethane interface between metal components — they allow controlled compliance while absorbing noise and vibration. Factory rubber bushings are soft by design to maximize ride quality and reduce NVH. This softness allows movement at mount points that translates to imprecision — the differential can shift under load, the transmission crossmember can deflect, and driveline angles can change. Replacing with tighter-durometer polyurethane eliminates this movement, producing a more precise and predictable chassis response.

Polyurethane Construction and Standalone Mount Upgrade

Polyurethane bushings transmit more noise and vibration than rubber — an inherent trade-off of the tighter durometer. On a street-driven performance car this NVH increase is generally acceptable. For track builds or builds where precision is the priority, polyurethane bushing kits are a meaningful upgrade wherever factory rubber introduces compliance. All Cobb bushing kits include the correct size and durometer for the specific mount location.

What’s in the Box

• Cobb bushing kit — Rear mount
• Installation hardware

Why Choose Cobb Tuning

Cobb Tuning has been developing performance software and hardware for turbocharged enthusiast vehicles since 1999. Founded in Austin, Texas, Cobb built its reputation on the Accessport and expanded into a full catalog of hardware engineered to complement it. Every OTS map is developed in-house on real vehicles, and every hardware product is validated as part of a complete system — not sourced and sold in isolation. That integrated approach is why Cobb produces consistent, reliable results across the builds we see every day.

The RallySport Take

The Cobb kit for the rear differential subframe mount bushing inserts is the targeted replacement for this specific mount location. Works standalone or as part of the complete Cobb Driveline Bushing Kit for the full driveline compliance reduction program.

Fitment

Year	Make	Model	Notes
2008-2021	Subaru	WRX	EJ255/FA20DIT
2008-2021	Subaru	WRX STI	EJ257