As if Tier 4 final wasn’t bad enough, here comes Stage 5 (Europe) which will end up being Tier 5 in the States. So now your muffler contains the DOC, DPF, DEF doser & mixer, and finally the SCR. It’s bad enough T/S’ing tier 4 engines (and there are three generations of tier 4) in class 8 trucks and industrial engines, now you have stage 5 coming fast. Complete garbage and always broken in some manner.
No way they pay enough anymore to work on these engines in trucks. It’s a young mans game and eventually they all grow to loath it. Stick to driving or equipment operator. Or look to the technical side. Electric or controls and automation is the way to go if you wanna wrench into things.