Just wondering what would be recommended. WKJeeps says 15,000 miles (24,000 km) for front and rear diffs at schedule B, my 2008 manual calls for 20,000km with the CRD and 30,000km with the gassers. 10,000km is quite a large difference and they don't give any real explanation.
Could the difference for the CRD's be due to the D44 used on the 2wd? I would have thought a CRD with QDII would have the same change interval as a Hemi with QDII considering we run the same axles...
Did a search but I couldn't anything answering this specific question.
30,000 km (18.75K miles) is an easy interval for non-Americans to remember, and it is not far off of 15K miles. 20,000 km (12.5K miles) is also not far off of 15K miles, but in the other direction.
CRD has more torque, and that extra torque probably has a tendency to kill the fluid faster. It is kind of like towing. Towing something is rougher on everything. Extra torque is also rougher on everything. Thus, 18.75K miles is probably not good enough for CRD. The next lower convenience point would be 12.5K miles.
I bet that all non-CRD vehicles could easily go out to 18.75K miles on fluid swaps without issue. However, that is not the easy to remember fluid swap interval point, and you would not want to wait until 30K miles. 30K miles is the big swap point, and half of that is the semi-big swap point. Everything between is supposed to be small.
Manufacturers cater to the lowest common denominator. That would be the people who do not write any of the records down and only use their odometer reading to figure out what is due. I keep track of everything for all four of our cars in Excel. I do the math such that if I get "off schedule," I just stay off schedule, rather than do a change early when it is not needed to get me back on to schedule.
I could understand the torque differences but don't the CRD and the Hemi run roughly equal in terms of torque? Although I'm sure they hit this point at different ranges. I'm currently sitting at just over 16,000 miles so maybe I'll just change it now. I had thought it would be 30,000km like every other model so I never really looked into it.