Austin-Healey 100

Manual transmission fluid capacity & service interval

Austin-Healey 100 manual transmission fluid capacity ranges from 2,3 to 3 liters. Service intervals occur every 6000 miles or 9600 km. The data covers 3 configurations.

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

TypeSpecifications
100/6, BN4 / BN6 (1957-1959)
  • Use: Normal
  • Capacity 2,3 liter
  • Capacity 3 liter (+ overdrive)
  • Change 6000 miles/ 9600 km
  • Code: 4/1
100/6, BN4 (1956-1957)
  • Use: Normal
  • Capacity 2,3 liter
  • Capacity 3 liter (+ overdrive)
  • Change 6000 miles/ 9600 km
  • Code: 4/1
  • 100/4, BN1 (1953-1955)
  • With overdrive
  • Use: Normal
  • Capacity 2,5 liter
  • Change 6000 miles/ 9600 km
  • Code: 3/1

Additional Notes

  • The Austin-Healey 100/4 BN1 (1953-1955) carries a single manual transmission fluid capacity of 2.5 liters, which covers both the standard gearbox and the overdrive unit together as one combined fill.
  • The 100/6 BN4 and BN6 variants list two distinct capacity figures: 2.3 liters for the standard manual transmission without overdrive, and 3.0 liters when the overdrive unit is fitted, reflecting the additional fluid volume the overdrive housing requires.
  • Across all three configurations spanning 1953-1959, the specified change interval is 6,000 miles or 9,600 km under normal use conditions, applying uniformly regardless of whether overdrive is present.
  • The 100/4 BN1 capacity of 2.5 liters sits between the two figures listed for the later 100/6 variants, meaning the BN1 combined transmission-and-overdrive fill is actually less than the 3.0-liter overdrive-equipped figure seen on the six-cylinder models.
  • The 100/6 BN4 appears across two separate row entries covering 1956-1957 and 1957-1959, with both rows sharing identical capacity values and the same 6,000-mile change interval, indicating no specification change occurred for that variant across those years.
  • A 6,000-mile fluid change interval was a relatively short service cycle by general automotive standards, consistent with the maintenance expectations of British sports cars from the 1950s operating under normal conditions.

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