OTC's Truck Pinion Sockets are designed and built to have the correct clearance for yoke and locknut assemblies on a variety of truck transmissions and differentials. No. 1977 is a 6 pt. socket with a 2-1/4 inch opening. To determine socket size needed, measure locknut from flat to flat. 4 inches long with 3 full inches of usable depth to give you plenty of clearance for all kinds of jobs. Using the right tool saves time and effort, eliminating the need to destroy standard sockets by grinding them down to fit tight pinion clearances. OTC locknut sockets are formed from high-strength steel that is resistant to rounding out under high torque loads. Designed for use with 3/4 inch, square-drive MANUAL tools only. NOT intended for use with impact tools - use with impact tools will void the socket. Value is at the core of the OTC tool and equipment portfolio. For a simple repair or the most complex drivability concern, these award-winning tools universally solve problems faster, and at better value, than any other product line available. Whether it’s a specialty tool or unique piece of service equipment, OTC provides top solutions to modern automotive service challenges while increasing technicians’ productivity and shop profits.