Didn't think about the worn crank, hopefully not too bad yet.It can be done. I don't know if its worth while because the crank will have wear as well. Worse case you will be out a set of bearings and a bunch of time.
If I was to pull motor, I would prolly just buy a long block replacement. If I can make it last another six months by doing this, I will do a swap next summer.It can be done, you may need to engineer a tool that fits into the oil channel in the crank to help remove the upper main bearing halves. Be sure to use lube on the new rms, it will tear otherwise. However I don't believe this is worth the effort. Let me explain.
If the knock is indeed a bearing issue, crank journal scoring is likely. To correct this scoring the crank journals should be resurfaced. I've seen two 4.0s with knocks, one was a wrist pin knock, the other was a broken piston skirt. I have not seen a 4.0 knock with a bearing issue, I'm by no means a 4.0 expert either. I'd highly recommend pulling the motor, and doing a full rebuild. It's the only way to be sure you have completely resolved the issue.
Did you see shavings in the oil? I have never found shavings in the oil. It doesn't knock all the time. I start it and no knock. When temp reaches 100 degrees it starts with a knock and then goes away after reaching full operating temp.bought a parts rig and can't bring myself to tear it apart since it's so clean. here was my knock. bore looks fine, mic'd the top bit not bottom. new piston, rod bearings and mains on the way. Doing it with the motor in.
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