Rear Differential
Automatic Torque Biasing Differential enables your car to accelerate quicker and corner faster.
The Differential powers both drive wheels under nearly all conditions. With an ordinary open differential (standard on most cars), precious power is wasted during wheel spin under acceleration. This happens because the open differential shifts power to the wheel with less grip, along the path of least resistance. The Differential, however, does just the opposite. It senses which wheel has better grip, and biases the power to that wheel. It does this smoothly and constantly, and without ever completely removing power from the other wheel.
Differential 20-80%
Manual cars only
Fits:
Porsche 996 Turbo
Porsche 997 Turbo
- Porsche 996 TURBO 2000-05
- Porsche 997 MK1 TURBO 2007-09

Fits:
Porsche 986 Boxster 1997 - 2004
Porsche 996 Carrera 1998 - 2005
Click 'Zoom in' for large parts diagram.
Diagram ref no 3
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
90030903801
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Outer Diameter: 54mm.
Fits:
Vehicles With Tiptronic Transmission (PR 249)
Porsche 986 Boxster 1997>>2004
Porsche 987.1 Boxster MKI 2005>>2008
Porsche 987.1 Cayman 2006>>2008
Porsche 996 Carrera 3.4L 1998>>2001
Diagram Ref No 3
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99639701500
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche Boxster 987 2.7L 2005 -08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08

Fits:
Porsche 986 Boxster / S 1999-04*
Porsche 996 Carrera 1998-05*
*Only for models with the six-speed manual transmission.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
996302122
The product you are viewing cross references to these numbers
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
Porsche Rear Differentials | Precision Power Distribution for Maximum Traction and Performance
The rear differential is one of the most critical components in your Porsche’s drivetrain. It transfers engine power from the transmission to the rear wheels while allowing them to rotate at different speeds during cornering. This ensures balanced handling, traction, and stability — essential for Porsche’s trademark driving dynamics.
At Design911, we supply high-quality rear differentials and differential components engineered to meet or exceed original performance standards. Built from precision-machined gears, hardened steel housings, and performance-grade bearings, each unit ensures smooth torque distribution and dependable strength under demanding conditions.
Whether you’re maintaining a daily driver or upgrading for track use, our Porsche rear differential parts deliver improved traction, cornering precision, and long-term reliability.
What Does the Rear Differential Do?
The rear differential balances rotational speed between the rear wheels while transmitting power from the gearbox to the axles.
Core Functions:
- Distributes torque evenly between rear wheels.
- Allows independent wheel rotation during turns.
- Prevents wheel slip and loss of traction.
- Reduces drivetrain stress and enhances stability.
- Supports optimal cornering control and handling balance.
Without a properly functioning differential, your Porsche may experience wheel spin, vibrations, or loss of power transfer — reducing both performance and safety.
Why Do Rear Differentials Fail or Wear Out?
Over time, continuous stress, torque, and heat exposure can cause differential components to wear, leading to poor lubrication and gear damage.
Common Causes of Failure Include:
- Low or contaminated differential oil causing friction and overheating.
- Bearing wear leading to excessive noise or vibration.
- Gear tooth pitting or chipping from torque overload.
- Seal failure causing oil leaks.
- Corrosion or fatigue from moisture intrusion.
Signs of a failing differential include whining noises, clunking on acceleration, fluid leaks, or uneven tyre wear.
Why Replace or Upgrade Your Porsche Rear Differential?
Replacing a worn or damaged differential restores power delivery, traction, and drivetrain balance. Upgrading to a performance-spec or limited-slip differential (LSD) enhances handling and control — ideal for spirited road or track driving.
Key Benefits:
- Restores smooth, balanced power distribution.
- Eliminates noise, vibration, and gear chatter.
- Improves traction and acceleration out of corners.
- Extends drivetrain longevity through precise engineering.
- Suitable for Porsche 911, Cayman, Boxster, Panamera, and classic models.
- Available in performance or standard specifications.
Replacing the differential during gearbox or axle servicing ensures long-term reliability and optimum drivetrain efficiency.
Highlights
- Premium Porsche rear differentials and components.
- Precision-engineered for torque balance and durability.
- High-strength materials for road, race, or restoration builds.
- Reduces noise, vibration, and harshness (NVH).
- Ideal for upgrades, rebuilds, or performance applications.
- Compatible with manual, Tiptronic, and PDK systems.