Sierra 18-9842 Drive Shaft Retainer Wrench The Sierra 18-9842 Drive Shaft Retainer Wrench is interchangeable with the following: GLM 90240, Mallory 9-79807, Mercury 91-43506T. Each Sierra product meets or exceeds the original equipment part it replaces. Sierra Drive Shaft Retainer Wrench Meets or exceeds the original equipment quality Sierra part number: 18-9842 Interchangeable with the following: GLM 90240, Mallory 9-79807, Mercury 91-43506T