RING-ADJUSTMENT 3D9552 - Caterpillar

D379, D398, D399 Engines Equipped With Woodward GovernorsAccording to field reports, some customers have had problems with failure of the governor linkage on the above engines. Most of the problems have been on generator set engines used in drill rig applications, where the frequency of linkage adjustment is high.
The linkage failures have been at the joints (connections) where the rod ends are assembled to the linkage rod. When the rod does not have enough threads engaged in either rod end, normal stresses can cause thread failure. This permits separation of the joint, and loss of governor control. The result can be high engine rpm (overspeed) and possible engine damage.
To prevent these possible failures, it is important to be sure the linkage rod and each rod end have enough threads engaged after assembly and/or adjustment of the linkage. This can be checked by use of the small (1.8 mm - .07" diameter) holes through the sides of each rod end. After the assembly or adjustment of the linkage is finished, put the end of a small wire, cotter pin, or other similar item into the hole in the rod end. If the rod is assembled far enough into the rod end to engage the minimum permissible number of threads, the hole will be closed by the end of the rod. If the hole is still open, not enough threads are engaged, and the rod must be assembled farther into the rod end. Also, be sure the nut is correctly tightened against each rod end to hold the rod in position and prevent possible thread wear from vibration.