Henry Heider's third tractor was released in 1914 as the Model C. This machine used a Waukesha engine and was a near complete redesign from previous models. Once again, Henry opted to utilize Rockwood's Friction Transmission, but in this case, the engine and flywheel (coated on the edge with friction material) could be slid forward or backward with the help of a lever (locking in seven positions), which changed the relative diameter of the transmission's driven wheel, effectively giving the tractor seven speeds. The Rock Island Plow Co. was impressed with the Model C and bought the tractor in large numbers, and in early 1916, negotiated purchase of Heider's tractor division – along with the services of Henry Heider.
Henry's relationship with Rock Island netted them the 2-plow Heider Model D in 1917, the Model 15-27 in 1925, and the sliding-gear transmission-equipped Model 18-35 in 1929. Henry resigned from Rock Island in 1922 shortly after working out much of the 18-35's design. Terms of the Heider-Rock Island agreement stipulated that the tractors carry the Heider name through 1927.
Meanwhile back in Carroll, Iowa, Heider Manufacturing Co. was still busy with horse-hitch parts, ladders and Henry's All American Coaster Wagon that initially featured fifth-wheel steering and, later, automotive-type steering. The company went on to produce farm wagons, feed wagons, running gear, truck boxes, hog feeders, farm gates and other items until it was sold to the Wellbuilt division of the Scranton Manufacturing Co. in 1983.