Mazda B, UN (USA / CAN)

Differential fluid capacity & service interval

Mazda B, UN (USA / CAN) differential fluid capacity ranges from 1,7 to 2,5 liters. The service interval for fluid replacement is 150000 miles. The data covers 7 configurations.

The configuration chart below lists fill volumes and service intervals for each engine and trim variant.

TypeSpecifications
  • B 2300 (2003-2007)
  • Rear
  • Use: Normal
  • Capacity 2,2-2,5 liter
  • B 3000 2WD (2003-2007)
  • Rear
  • Use: Normal
  • Capacity 2,2-2,5 liter
  • B 3000 4WD (2003-2007)
  • Front
  • Use: Normal
  • Capacity 1,7 liter
  • Change 150000 miles
  • Code: (4x4)
  • B 3000 4WD (2003-2007)
  • Rear
  • Use: Normal
  • Capacity 2,2-2,5 liter
  • B 4000 2WD (2003-2007)
  • Rear
  • Use: Normal
  • Capacity 2,2-2,5 liter
  • B 4000 4WD (2003-2007)
  • Front
  • Use: Normal
  • Capacity 1,7 liter
  • Change 150000 miles
  • Code: (4x4)
  • B 4000 4WD (2003-2007)
  • Rear
  • Use: Normal
  • Capacity 2,2-2,5 liter

Additional Notes

  • The rear differential capacity across the Mazda B, UN (USA / CAN) lineup — covering the B 2300, B 3000 2WD, B 3000 4WD, B 4000 2WD, and B 4000 4WD — is listed as a range of 2.2–2.5 liters rather than a fixed value, which reflects normal variation during a service fill depending on the unit's drain level and housing geometry.
  • A capacity expressed as a range, as seen with the 2.2–2.5 liter rear differential figure, is characteristic of a service fill specification rather than a dry or overhaul fill, where a precise maximum volume would typically be stated.
  • The front differential on the B 3000 4WD (2003-2007) holds a fixed 1.7 liters, a notably smaller volume than the rear differential on the same configuration, consistent with the compact housing typical of front differentials integrated into 4WD transfer arrangements.
  • The front differential on the B 4000 4WD (2003-2007) shares the same 1.7-liter capacity and 150,000-mile change interval as the B 3000 4WD front differential, indicating a common front axle assembly across the two engine variants in 4WD trim.
  • A 150,000-mile change interval is specified for the front differential fluid on both 4WD configurations under normal use conditions, placing front differential service among the least frequent fluid maintenance tasks in the lineup.
  • No change interval is listed for the rear differential across any configuration in the 2003-2007 range, while the front differential on 4WD models carries an explicit 150,000-mile interval, making the front and rear differential service schedules structurally different within the same vehicle.
  • The 2WD variants — B 3000 2WD and B 4000 2WD — carry only a rear differential entry with no front differential specification, which aligns with the absence of a front axle drive unit in two-wheel-drive drivetrain layouts.

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