M142

The Typ 320 replaced the Typ 290 in February 1937, and its six was the older car's 2.9-liter unit opened up: the bore went from 78 to 82.5 mm, the crankshaft gained twelve counterweights in pursuit of refinement, and a Solex dual downdraft carburetor replaced the predecessor's updraft type. Buyers could specify cylinder heads of different compression depending on whether they ran straight petrol or a petrol–benzole mix. Behind it sat a four-speed gearbox with synchromesh on every ratio, unusual for the 1930s, in place of the 290's overdrive arrangement.

Then German fuel quality began to slide. In early 1939 the bore was opened another 2.5 mm to 85 mm, lifting capacity to 3,405 cc for no gain in output — the extra swept volume simply bought back what poorer petrol was taking away. Model, chassis and engine designations all stayed as they were; only the Wehrmacht Kübelwagen version was renamed 340. Of the 6,861 cars built through to the final Untertürkheim examples in November 1942, 1,764 were bucket-seat military variants, some with engines rated at 80 PS.