Dodge Sprinter Rear Differential Fluid Change
-Oil drain tray
-Fill Tool or homemade funnel
As with any fluid change it is a lot easier if the fluid is warm, so driving around before draining it is helpful.
Set up an oil drain tray below the rear differential. Using the 14mm socket remove the drain screw. It is located on the lower passenger side of the differential, facing the rear passenger side tire. I used an impact gun to remove it and it was on there really good. If you do not have that I would recommend a breaker bar. Once removed let the fluid drain out for a while.
Once it is completely drained reinstall the drain plug. To fill you simple remove the rubber grommet and fill till it comes out that hole... easier said than done. The diff is in an awkward place so it is hard to do. I used a homemade funnel, but they sell tools like this which would make it much easier.
Fill till the fluid comes out the hole and let it drain out. Once it stops draining replace the grommet.
There is a lot of debate on the fluid type. I used Fuchs 80w-90 diff fluid. If you are curious about it this forum thread has a lot of info and opinions on what fluid to use.