Mechman 400 Amp Machined Billet Alternator for Nissan & Infiniti 2.5L 3.5L 3.7L 4.0L 5.6L B11256400M

This 400-amp high-output alternator is engineered for demanding Nissan applications where consistent, high-current power is critical. Designed for vehicles running large audio systems, auxiliary electronics, winches, lighting, and other high-draw accessories, it delivers stable voltage under load where factory charging systems fall short.

Built in the USA using premium components, this alternator is designed for continuous high-amperage output with reliability as the priority. Strong idle output and a broad usable RPM range help maintain voltage stability during real-world driving conditions, not just at peak engine speeds. Each unit is hand-assembled and tested to ensure consistent performance and long service life.

Like most high-output alternators, this unit is equipped with a smaller overdrive pulley to help maintain maximum output at idle and will typically require a belt that is 1/2 inch to 1 inch shorter than the factory belt to achieve proper belt tension.

To simplify installation, the alternator includes a dedicated adapter plug. One side connects directly to the alternator, while the opposite side plugs into the factory vehicle harness, allowing for a clean, plug-and-play electrical connection without modification to the OEM wiring.

Features include:

• 400 amps of peak output for extreme electrical demand
• Strong idle output and improved voltage stability under load
• Overdrive pulley included to enhance low-RPM performance
• Plug-and-play adapter harness included for direct factory connection
• Heavy-duty internal components designed for sustained high-current operation
• Direct-fit design for select Nissan applications
• Ideal for high-power audio systems, off-road accessories, lighting, and auxiliary power needs

*Attention!* Nissan Titan Owners

The 2007 Nissan Titan had a mid-year change where two different alternators were used. Please reference the image and verify that the regulator plug matches your factory alternator before ordering.

For Nissan owners pushing serious electrical loads, this Mechman 400-amp alternator delivers dependable, high-output charging performance built for both daily use and demanding environments.

Fitment Table | B11256400M – Plug Code: 325

Installation Notes:

This unit comes equipped with a smaller 1.75-inch diameter alternator pulley and will require a slightly shorter drive belt for proper belt tension.  Not recommended for sustained use above 5,000 RPM engine speed. If a larger pulley is required, please reach out to Mechman’s support team and we can work to get you an underdrive pulley to meet your RPM demands.