If you do look at the rams, I would check the hvac controls. The actuators commonly break leaving you with only defrost. It's an expensive fix. The only other problem I had was the number 4 injector line. It's isolator rattles loose and vibration cracks the high pressure line right at the barrel but that threads into the common rail. Search for it... It's a 27$ part from cummins and takes about 20 minutes to change. If it does crack it incapacitates the truck.
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