The  Rear-Drive Drum employed on Grey tractors provided superior traction that boosted field performance.

Gray Tractor Company’s model 18-36, first sold in 1916.  It was the first tractor evaluated at the Nebraska Tractor Test to burn gasoline and to use the unique rear drum-drive system.  The later design allowed the 18-36 to pull a four-bottom (14 in.) plow utilizing only a 32 brake hp. engine.  The motor, a four cylinder, 4 3/4 x 6 3/4 inch Waukesha-built unit, was also unique in that it was mounted crossways to the tractors frames.  A chain-driven transmission offered speeds of 1 1/2 and 2 mph.  Sale price for the 18-36 was $2150.00  The Minneapolis, Minnesota-based firm also sold the models 20-35, 18-30, and 22-40 before ceasing tractor production in 1933.