I got the diff fluid changed out to 85 140 with blue devil rear main seal .

seafoam did the trick on the engine removed the sludge so I was able to change the oil. Running good now.

 

Next up for the 2500 rig
shuttle valve
lift
tires

 

I often see a catalyst efficiency below threshold code when i'm troubleshooting for plugged catalytic converters. That is a fairly big clue and it is set by the difference between the upstream and downstream O2 sensors. Where it may just be a bad O2 sensor it can also be an actual plugged or bad converter. Not definitive but a good clue as to where to look. Obviously the visual inspection is a better test of the converter.