I found the Cat diagram of the trunnion of my Cat D3G. It shows that there is a bearing on the trunnion pin that secures the blade to the c-frame. How do you determine when the bearing and/or pin needs to be replaced?
You first determine if you have excess movement in the joint. If there is excess movement then you should remove the cap, remove the shims, re-install the cap (run the bolts up so that the cap gap is even on both sides) and measure the gap between the caps. Replace with how many shims are required to fill the gap, then add one more shim between each side of the caps.
If the caps meet without any shims then it is time to replace parts.
I notice on my machine that the trunnion ball is attached to the middle of a pin. The pin is welded to the c-frame at the top and bottom of the pin which stands up-right. How is the ball attached to the pin or is the pin and ball all one part? If the ball and pin are integrated into one part, do you have to cut the pin and ball out and weld the new one in?