The S-4 is a conventional straw-walker combine harvester, and has front-wheel drive. The front axle has a track width of approximately 2400 mm, the rear axle has a track width of approximately 910 mm. The engine torque is sent through a manual four-speed gearbox with an additional two-speed reduction gearbox, and from the gearbox output shaft to the front axle with a belt. The belt's length is fixed, thus not allowing continuous variable driving speed. The corn passes through the S-4 in longitudinal fashion. It enters the combine in front, and gets pulled into the mid-mounted threshing drum; the straw exits the machine in back, after getting cleaned in the straw walkers installed in the S-4's rear compartment. Both four-metre and three-metre headers, hydraulically adjustable in height from 60 to 700 mm, were available for the S-4. The reel, cutter bar, header auger and corn conveyor are driven mechanically by belts and chains. The reel speed can be adjusted by swapping cogwheels in the header drivetrain, but the S-4 does not have fine reel speed adjusting. The threshing drum has a width of 865 mm and a diameter of 550 mm. It is equipped with 8 rasp bars. It is driven by a belt, that is hydraulically adjustable in length (
continuously variable transmission), in order to adjust the threshing drum speed. The speed is adjustable between 385 und 1350 min−1. The concave's distance from the threshing drum can be adjusted with three turnbuckles. The S-4 has four straw walkers, and two adjustable sieves. The corn tank holds up to 1300 kg of corn. The original S-4 is powered by a 5.6 litre, 39 kW ZIS-120 otto engine. This engine has a very high fuel consumption of 18–20 litres per hour and was not well-suited for East Germany. East German Fortschritt E 170 series combines were instead fitted with the IFA EM 4-15-5 diesel engine, a swirl-chamber injected 6.024 dm3 four-cylinder unit, producing 40 kW at 1500/min. Its peak power is up to 44 kW. The engine is mounted in front, next to the driver's seat. == Fortschritt models ==