BT-20 Navistar Four Square Test for Gear Lubricants
Tractors, backhoes, excavators, forklifts and other heavy duty equipment may rely on hydrostatic transmissions (continuously variable transmissions) to transmit power from hydraulic shafts to gear boxes. For optimal performance, these systems require specially formulated hydraulic transmission fluids. This test, also known as the FZG test (ASTM D5182), simulates a tractor gear box to determine the load carrying capacity of these fluids.
The pinion and gear system specified in the method is assembled, filled with lubricant, and run for a break-in period. The torque is increased, the system is run for the number of cycles at the rotations per minute specified in the method, and the pinion and gear disassembled and inspected. This process is repeated at varying conditions as per the method. Reported is pitting or tooth breakage on the gear and pinion for each run.