A new model code system was taken to use gradually starting from 1977, of which high variant was SM. SC was an especially low model. The conventional cabin models were low SL and SN and the high SR. The number was not a running model number any more, but indicated the engine output in kilowatts. In the later models the value was rounded in accuracy of ten. The engine code letters was added at the end. This was followed by letter H if the vehicle was equipped with more than two axles.