BMW F20 F21 M135i N55 Petrol Automatic Gearbox 8601209 GA8HP45Z WARRANTY

Listing details

The gearboxes are sold with a 90-day warranty! They were tested before removal and are in full working order.

BMW F20 F21 M135i N55 Petrol Automatic Gearbox is a factory-original, used automatic transmission designed for the sporty 1 Series versions with the N55 petrol engine. Thanks to its precise construction and optimized control, it ensures smooth gear shifting, high durability, and stable torque transfer under demanding road conditions. This is a solution for users who expect to maintain the original characteristics of the drivetrain and ensure proper communication with the vehicle's electronics.

Specifications and technical data

• SKU: 8601209
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 8601209
• Substitutable numbers: 8601209, 24008601209, 7647345, 24007647345
• Fuel type: Petrol
• Gearbox type: Automatic
• Category: Automatic Transmission

Purpose and technical characteristics

The presented gearbox belongs to the Automatic gearboxes group for BMW and has been designed to work with the N55 petrol engine in F20 and F21 models in the M135i version. The Automatic design ensures fully automated gear shifting, with the possibility of dynamic use of the engine's power while maintaining comfort during daily operation. The applied GA8HP45Z architecture is widely used in the BMW range, which translates into good service availability and proven design solutions.

Operating parameters and performance features

The gearbox has been developed with Petrol engines in mind, which means appropriate gear ratios tailored to the torque characteristics of the N55 unit. The automatic transmission system ensures:

• smooth gear shifting during relaxed driving,
• faster throttle response in dynamic mode,
• stable power transfer under higher loads,
• optimal engine RPM across a wide speed range.

Thanks to this, the gearbox performs well both in daily city use and during more demanding highway driving or dynamic maneuvers characteristic of the M135i version.

Vehicle integration and installation aspects

As a component dedicated to the BMW F20/F21 M135i series, the GA8HP45Z automatic gearbox is designed for full integration with the vehicle's factory systems. This includes compatibility with:

• electronic engine and drivetrain control units,
• traction and stability control systems,
• driving modes (comfort, sport – depending on the car's configuration).

Such compatibility reduces the risk of communication issues between modules and allows for the preservation of the manufacturer's original settings. A used gearbox with preserved OEM structure is a good choice when replacing a damaged transmission if the goal is to restore factory operating parameters without structural modifications.

Application in the BMW M135i drivetrain

In the sporty M135i version, precise transfer of the petrol engine's power to the wheels is crucial, and the GA8HP45Z automatic transmission is responsible for maintaining the appropriate gear ratios depending on load and driving style. Properly selected gear ratios allow to:

• maintain the flexibility of the N55 unit in the mid-RPM range,
• limit unnecessary downshifts during relaxed driving,
• ensure quick reactions when the accelerator pedal is pressed firmly.

Thanks to this, the car retains the character typical of BMW – a combination of automatic comfort with distinct sporty dynamics, which is particularly important in versions marked with the M symbol.

Choosing a used automatic gearbox and technical support

When choosing a used automatic gearbox for a BMW, it is worth paying attention to compatibility with the specific engine version, fuel type, and drivetrain configuration. It is also helpful to compare the OEM part number and interchangeable numbers, which are detailed in the product's technical specification. For users who want to deepen their knowledge about typical faults and the principles of safely purchasing a transmission from the secondary market, a practical guide has been prepared: Gearbox: manual, automatic, or DSG – typical faults and a guide to buying a used gearbox.

If you are planning a comprehensive repair or upgrade of the drivetrain area in your BMW and need other elements from the same group, such as complete transmissions, control components, or additional mounting parts, check the available parts in the BMW automatic gearboxes category.