GM-51162 is used to determine the backlash between the balance shaft gear and the crankshaft gear, and to position the balance shaft assembly housing to the crankshaft properly. The balance shaft assembly must be properly positioned to prevent noise during operation. Once the crankshaft is locked into the timing position at TDC, GM-51162-1 is attached to the balance shaft end. A dial indicator mounted to the engine block is aligned against the arm of GM-51162-1 at a specific location, and the arm is moved to determine the total travel of the arm and the gear backlash. GM-51162-2 is used to preload the balance shaft assembly to the crank gear, and starting at zero lash, is gradually backed off to control the backlash