VALVE GP-MAIN CONTROL 3350550 - Caterpillar

Introduction
The problem described below does not have a known permanent solution. Until a a permanent solution is identified, see the following directions.Problem
The circle drive mounting bolts on certain 16M Motor Graders have experienced loosening. The circle drive mounting bolts on certain 16M 3 Motor Graders and 18M 3 Motor Graders may experience loosening.Improper torque of circle drive mounting hardware during field repairs and/or damaged or worn threads in the draw bar are the most common causes of fastener loosening.Improper circle drive oil and improper circle drive slip clutch setting causes excessive loading of the bolted joint which can lead to fastener loosening.Solution
Ensure that all circle drive mounting hardware is installed. Any hardware that is found loose or missing must have the corresponding threaded hole inspected for thread wear using a check gauge. Bolts must be torqued correctly. Use of an impact tool when reassembling must be followed with proper torque procedures. Thread locker can be applied to fasteners as a precaution.If your machine has experienced bolt loosening, verify the circle drive oil type and viscosity as well as the circle drive slip clutch settings are correct. For oil specification, see the Operation and Maintenance Manual for your machine.Early 16M Motor Graders may be updated to the more serviceable circle drive mounting design. The new mounting design uses additional hardware which improves the bolted joint performance and reduces the time to remove the circle drive from the unit. Refer to Special Instruction , REHS9813, "Instructions for Reworking the Drawbar and Circle Drive Mounting on Certain 16M Motor Graders".Note: Later production16M Motor Graders and all 16M 3 Motor Graders and 18M 3 Motor Graders have the updated adapter plate installed from the factory.