GM-42991 is required to remove and install the front strut rod nut. The design of GM-42991 allows the use of a socket to hold the strut shaft (GM-39642) while using GM-42991 to properly remove and install the strut rod nut. Attempts to service the front strut rod nut without GM-42991 may result in increased labor time, improper tightening of the strut rod nut and/or component damage.