The production began in 1969 as a part of Suomen Autoteollisuus (SAT) and the first vehicles were based on lorry components.

[2] In 1970 SAT started a development project jointly with consulting company Jaakko Pöyry for suitable vehicles for loading and unloading of ro-ro vessels.

A significant feature was its patented fifth wheel coupling system which enabled a quick a flexible engagement.

[2] In autumn 1980, Sisu TR-200, which was the world's strongest terminal tractor by then, was presented in Portex fair in Hamburg.

The Sisu terminal tractors could be designed relatively easily according to the customer requirements due to highly modulised structure; this led to success in export markets in particular.

[2] When Sisu Corporation was created as a consequence of merger between the owning Sisu-Auto and Valmet wheeled machines, STS became a limited liability company (Oy).

At the same time Partek bought the Swedish container handling equipment producer Kalmar Industries, into which STS was joined.