The fourth-generation Dyna went on sale in August 1977. While the previous Dyna and the Daihatsu Delta shared some of the components, the two became identical at this model change, with Toyota supplying the vehicle under an OEM arrangement. The vehicle was also supplied to Hino Motors as the Hino Ranger 2. Responding to the market's demand for better economy and transport efficiency, the fourth-generation Dyna improved its diesel engine, ease of use, ride comfort, and maneuverability.


The previous semi cab-over-engine styling was replaced with the full cab-over-engine design, resulting in a boxy and more spacious cabin, and shortening the wheelbase by 310 mm to 2,800 mm, although the vehicle length remained unchanged. Consequently, the minimum turning radius was reduced from 5.7 m to 5.2 m.

To enhance safety, an exhaust brake was employed on 2.5- and 3-ton models, and the brake performance was enhanced for all models. A tilt-cab mechanism was also introduced to improve serviceability. In September 1980, a wide-cab, long-body model was added to the lineup, featuring a 300 mm wider cabin and a 4,310 mm cargo bed that was the longest in class. The fourth-generation Dyna continued to add various improvements and remained in production until August 1984.