The rear differential is a critical part of the BMW G8X M2, M3, and M4 drivetrain, transferring engine torque through the driveshaft and rear axle shafts while absorbing substantial loads during acceleration, braking, gear changes, and hard cornering. As power levels increase and suspension modifications become more aggressive, controlling differential movement and maintaining appropriate drivetrain geometry become increasingly important.

MMX Performance offers a modular solution for G8X owners with its Rear Differential Billet Front Cradle / Height Adjustable Mount Set (MMR55-1604) and Rear Differential Raised Poly Bush (MMR55-1605). Together, these components provide a more rigid differential mounting arrangement while allowing the differential position to remain at the factory height or be raised by 10mm.

Designed specifically for the BMW G87 M2, G80/G81 M3, and G82/G83 M4, the MMX system provides a direct-fit upgrade for vehicles ranging from street-driven builds to high-power and track-focused applications.

Controlling Differential Movement in the G8X Chassis

The factory differential mounting system uses rubber components that allow a degree of movement as the differential responds to drivetrain loads. Some movement is necessary in a road car, but increased power, aggressive driving, and track use can place substantially greater loads through the mounting points.

Excessive differential movement can affect how consistently the drivetrain remains positioned relative to the chassis and can become more noticeable during hard acceleration, rapid gear changes, braking, and aggressive cornering.

The MMX Performance mounting components are designed to provide a more controlled connection between the rear differential and chassis. By increasing mounting rigidity and reducing unnecessary movement, the system helps maintain more consistent differential positioning under load.

Rather than relying on a single solid mounting solution, MMX has developed a modular system that can be configured according to the vehicle's suspension setup and intended use.

MMX Performance G8X Billet Front Differential Cradle — MMR55-1604

The foundation of the system is the MMX Performance G8X Rear Differential Billet Front Cradle / Height Adjustable Mount Set, MMR55-1604.

Designed as a direct replacement for the factory front differential cradle, the MMX unit is precision-machined from 6061-T6 billet aluminum. This rigid construction provides a significantly more substantial mounting structure than the factory component while maintaining the original differential mounting location.

The billet cradle is engineered to withstand the increased loads associated with high-performance and track-driven G8X vehicles while providing a durable solution for the factory mounting position.

Precision 6061-T6 Billet Aluminum Construction

The MMR55-1604 is manufactured from 6061-T6 billet aluminum, combining strength, rigidity, and precise machining in a single component.

Billet construction allows MMX to produce the cradle with accurately machined mounting surfaces and a rigid structural design. This helps establish a more secure connection between the differential and chassis while maintaining the direct-fit nature of the upgrade.

For G8X owners running increased power, upgraded drivetrain components, or frequent track use, controlling differential movement becomes particularly relevant as drivetrain loads increase.

Factory Differential Height or +10mm Raised Position

One of the most important features of the MMX front cradle is its ability to work with the differential at different heights.

When the MMR55-1604 billet cradle is used by itself, the differential remains in its factory position.

When it is combined with the MMX Rear Differential Raised Poly Bush, MMR55-1605, the differential can be positioned 10mm higher than stock.

This adjustment provides an important advantage for G8X vehicles equipped with lowered suspension.

Why Raise the Differential on a Lowered G8X?

Lowering a vehicle changes the relationship between the chassis, differential, driveshaft, and rear axle assemblies.

As ride height decreases, the differential remains in relation to the chassis while the suspension and axle geometry changes. This can increase the operating angles of drivetrain components, including the axle shafts and CV joints.

The MMX system's +10mm differential position allows the differential to be raised closer toward its original relationship with the chassis and rear axle assemblies.

This can help reduce the operating angles created by lowering the vehicle and restore drivetrain geometry toward its original position.

For G8X owners running lowering springs, coilovers, or other suspension modifications, this provides a way to address differential positioning as part of the overall suspension and drivetrain setup.

MMX Performance Rear Differential Raised Poly Bush — MMR55-1605

The MMX Performance Rear Differential Raised Poly Bush, MMR55-1605, complements the billet front cradle by providing a height-adjustable rear differential mounting point.

Unlike a conventional replacement bush that maintains a fixed mounting position, the MMR55-1605 features an adjustable center section that allows two different differential positions:

OEM factory height or +10mm raised height.

This makes the bush suitable for both factory-height G8X vehicles and lowered vehicles where differential positioning and drivetrain geometry need to be considered.

Polyurethane Construction for Increased Mounting Control

The MMR55-1605 uses a high-quality polyurethane construction to provide a more controlled connection between the rear differential and chassis.

Compared with the movement permitted by the factory rubber mounting arrangement, the polyurethane bush is designed to reduce unwanted differential movement during acceleration, braking, gear changes, and other drivetrain loading conditions.

This provides a more controlled differential mounting arrangement without requiring the vehicle to use an excessively aggressive solid mounting solution.

MMX has also designed the bush to minimize additional noise, vibration, and harshness (NVH) compared with more aggressive solid mounting approaches, making it suitable for both performance street cars and track-focused G8X builds.

Two-Position Height Adjustment

The MMR55-1605 can be configured at either the OEM differential height or +10mm raised position.

The OEM position is appropriate when maintaining the factory differential height is preferred.

The +10mm position is particularly useful for lowered vehicles, allowing the differential to be repositioned upward to help compensate for the geometry changes created by reduced ride height.

When the front cradle and rear bush are used together, both components should be configured to the same differential height.

This means the complete three-point mounting configuration can be run at either:

• OEM differential height
• +10mm raised differential height

Designed Around the G8X Differential Mounting System

The MMR55-1604 and MMR55-1605 are not simply isolated replacement components. They form the foundation of an expandable MMX Performance G8X differential mounting system.

The components can be used together to create a three-point differential mounting configuration, or additional MMX hardware can be added to create a four-point arrangement.

This modular design allows G8X owners to configure the rear differential mounting system according to their vehicle's power level, suspension setup, and intended driving environment.

MMX 3-Point Differential Mounting Configuration

The basic MMX configuration combines the billet front cradle with one adjustable rear differential bush.

The required components are:

• 1x MMX G8X Billet Front Differential Cradle — MMR55-1604
• 1x MMX G8X Rear Differential Raised Poly Bush — MMR55-1605

This creates a 3-point differential mounting configuration.

Both components can be configured at the same differential height, allowing the complete system to remain at the OEM position or raise the differential by 10mm.

For a lowered G8X, the +10mm configuration can help address the drivetrain geometry changes associated with reduced ride height.

MMX 4-Point Differential Mounting Configuration

For owners looking for additional differential mounting control, MMX also offers its Dual Differential Mount, MMR55-1606.

When combined with the billet front cradle and two MMR55-1605 rear bushes, the system creates a 4-point differential mounting configuration.

The complete setup consists of:

• 1x MMX G8X Billet Front Differential Cradle — MMR55-1604
• 2x MMX G8X Rear Differential Raised Poly Bushes — MMR55-1605
• 1x MMX G8X Dual Differential Mount — MMR55-1606

The additional rear mounting location provides another point of control for the differential, helping further limit unwanted movement under high drivetrain loads.

For correct operation of the height-adjustable system, the mounting components should be configured consistently at either the OEM height or +10mm raised position.

Choosing One or Two MMR55-1605 Bushes

The MMX Rear Differential Raised Poly Bush is available in configurations using either one or two bushes.

A single bush is suitable for the three-point configuration when paired with the MMR55-1604 billet front cradle.

Two bushes are required when building the complete four-point configuration with the MMX Dual Differential Mount.

This allows owners to purchase the appropriate number of mounting points for their intended setup rather than replacing components that are not required for their configuration.

Maintaining Drivetrain Geometry on Lowered G8X Builds

Lowering a BMW G87 M2, G80/G81 M3, or G82/G83 M4 can improve the vehicle's stance and alter its suspension geometry, but reducing ride height also changes the relationship between drivetrain components.

The differential is connected to the driveshaft and rear axle assemblies, meaning its position plays a role in the operating angles of these components.

The MMX +10mm configuration provides a way to raise the differential relative to its standard mounting position.

This can help bring the axle shafts and CV joints closer to their original operating angles on a lowered vehicle, potentially reducing the additional stresses associated with unfavorable drivetrain geometry.

The adjustment is therefore particularly relevant for G8X builds where suspension modifications have significantly changed ride height.

A Modular Approach to G8X Differential Upgrades

The MMR55-1604 and MMR55-1605 can also form part of a broader rear differential upgrade package.

MMX offers additional G8X components that can be combined with the mounting system, including the:

• MMX G8X Dual Differential Mount — MMR55-1606
• MMX G8X Billet High-Capacity Differential Oil Pan
• MMX G8X Rear Differential Output Shaft Heat Shield Set

These products address different aspects of the rear differential system, allowing owners to build a more comprehensive solution around their specific vehicle.

The mounting components focus on differential positioning and movement control, while the additional MMX products address differential mounting points, fluid capacity, and thermal management.

Direct-Fit Installation

Both the MMR55-1604 billet front cradle and MMR55-1605 rear differential bush are designed around the factory G8X differential mounting locations.

The billet cradle is a direct replacement for the factory front differential cradle, while the polyurethane bush replaces the factory rear differential mounting bush.

The installation does not require cutting, drilling, or permanent chassis modification.

For the +10mm configuration, the MMR55-1605 adjustable center section is positioned at the raised setting during installation.

When using the complete three-point or four-point system, the mounting components should be configured consistently to maintain the desired differential height.

Professional installation is recommended when performing differential mounting work, particularly when installing the complete four-point configuration or combining the system with other drivetrain and suspension modifications.

G8X Applications

The MMX Performance differential mounting components are designed specifically for the BMW G8X platform.

BMW G87 M2

• BMW G87 M2

BMW G80 / G81 M3

• BMW G80 M3
• BMW G81 M3 Touring

BMW G82 / G83 M4

• BMW G82 M4
• BMW G83 M4 Convertible

This makes the MMX system applicable across the current G8X M2, M3, and M4 family.

Street, Performance, and Track Applications

The MMX differential mounting system is designed for a wide range of G8X applications.

For street-driven cars, the polyurethane rear bush provides additional differential control while retaining a more street-oriented mounting solution than a completely solid setup.

For modified cars producing increased power, reducing unwanted differential movement can become increasingly important as drivetrain loads rise.

For track-focused G8X vehicles, the more comprehensive three-point or four-point mounting configurations can provide additional differential control while allowing the differential to be positioned appropriately for the vehicle's suspension setup.

The +10mm adjustment is particularly relevant to lowered cars, while factory-height vehicles can retain the OEM differential position.

Key Features of the MMX G8X Differential Mounting System

The MMX Performance MMR55-1604 Billet Front Differential Cradle provides:

• Application-specific design for BMW G87 M2, G80/G81 M3, and G82/G83 M4
• Precision-machined 6061-T6 billet aluminum construction
• Direct replacement for the factory front differential cradle
• Increased differential-to-chassis rigidity
• Improved control of differential movement under drivetrain loads
• Factory differential height when used independently
• Compatibility with the MMX MMR55-1605 raised polyurethane bush
• Support for a 10mm raised differential position when paired with MMR55-1605
• Direct-fit installation
• No cutting, drilling, or permanent vehicle modification
• Compatibility with the MMX MMR55-1606 Dual Differential Mount
• Suitable for street, performance, and track applications

The MMX Performance MMR55-1605 Rear Differential Raised Poly Bush provides:

• Application-specific G8X design
• High-quality polyurethane construction
• Direct replacement for the factory rear differential bush
• Two-position adjustment
• OEM factory height
• +10mm raised height
• Improved differential movement control
• Support for lowered G8X vehicles
• Helps compensate for altered drivetrain geometry
• Helps optimize axle shaft and CV joint operating angles
• Designed to minimize additional NVH compared with more aggressive solid mounting solutions
• Compatibility with OEM and aftermarket axle shafts
• No chassis modification required
• Designed for MMX three-point and four-point differential mounting configurations

Build the G8X Differential Mounting System Around Your Setup

The MMX Performance G8X differential mounting components provide a flexible way to improve differential control while accounting for one of the most important variables on a modified G8X: ride height.

The MMR55-1604 billet front cradle establishes a rigid, precision-machined mounting point at the front of the differential, while the MMR55-1605 adjustable polyurethane bush provides controlled rear mounting with the ability to retain OEM height or raise the differential by 10mm.

Used together, they create the foundation for a three-point differential mounting system. Adding the MMR55-1606 Dual Differential Mount and a second MMR55-1605 bush expands the setup into a four-point configuration for additional differential control.

For lowered G87 M2, G80/G81 M3, and G82/G83 M4 builds, the +10mm configuration also provides a way to address the drivetrain geometry changes associated with reduced ride height.

With direct-fit installation, no permanent chassis modifications, and compatibility with additional MMX differential upgrades, the system provides a modular solution for building a more controlled and properly positioned G8X rear differential assembly.

Related MMX Performance G8X Products

• MMX Performance G8X Rear Differential Billet Front Cradle / Height Adjustable Mount — MMR55-1604
• MMX Performance G8X Rear Differential Raised Poly Bush — MMR55-1605
• MMX Performance G8X Dual Differential Mount — MMR55-1606
• MMX Performance G8X Billet High-Capacity Differential Oil Pan
• MMX Performance G8X Rear Differential Output Shaft Heat Shield Set

Billet Cradle: https://x-ph.com/mmx-performance-g8x-rear-differential-billet-front-cradle-height-adjustable-mount-set-mmr55-1604/ 

Raised Polyurethane Bushing: https://x-ph.com/mmx-performance-g8x-m2-m3-m4-rear-differential-raised-poly-bush/