As you can see from the pictures, the damage to the cylinder block was
not caused by over-torque (the splines are intact), but rather by shaft
misalignment, caused by malfunction (better destruction) of the tail
bearing, and then the front bearing. This particular Caterpillar uses
two motors to turn the boom, that's why the initial torque loss signals
were masked up until the major failure occurred. When you find your
machine making strange noises or loosing force "just a little", don't
let it come to the catastrophic failure point, do something about it, it will be cheaper and
cause less downtime in the long run.
