Loud ticking noise around engine and jerking sometimes while shifting

Welcome to 2CarPros.
The 3.6 in your Journey has a few known issues.
One of them is rocker arm failure, specifically the bearing in the roller that rides on the camshaft fails and you hear a clicking sound. Usually, if you can hear it you will need at least that rocker and the camshaft. Possibly more.
Another issue is the flex plate between the engine and transmission cracks and causes noises. Both of these can cause it to go into limp mode. There are a few others but none that generate noise until they fail completely, then the noise usually comes from the owners mouth, and isn't pleasant to hear. First thing to do would be to scan the system for power-train codes. This will give you a place to start. Another test would be to take a piece of hose or a mechanics stethoscope and use it to listen to the various parts of the engine and follow the tick to it's source. That would get you at least in the area of failure and if it's around the transmission and not the engine it will help narrow it down. If possible could you record a video of the noise close in to the engine and another toward the transmission and upload them here? That may also help us give you a better idea of the fault.