If it is only "shuddering" or "chattering" in turns, try adding special low viscosity fluid (from Ford).
You can usually buy rebuilt parts from a salvage yard or a repair shop associated with a salvage yard. You can also buy these through the internet.
If there is not a drain plug on the bottom of the differential then you will have to remove the rear cover. If that is the case you will need a cover gasket. If it is limited slip, then it will require a special additive. Also be sure of the weight and if it is synthetic or not.
replacing 2003 fore explorer sport front wheel bearings
Repair Rear Differential Parts
The cost to repair the brakes on a 2003 Ford Explorer depends on the brand of the brakes, and the person/shop doing the repair. It can generally run between $70 and $200+ depending on those variables.
Ford Explorer Column Shifter Lever Bracket Repair
140 x 6
75w140 synthetic with limited slip additive.
Do a Google search of Ford Explorer blend door , there are lots of articles and some videos
( 5 w 20 ) for the 4.6 liter V8 engine in a 2003 Ford Explorer , according to the Owner Guide
approx. 100 dollars w/ seal, differential cover gasket material (RTV) and labor
The factory method requires removal of the dash and heater box to replace the plastic door with another plastic door. HeaterTreater has a new product to repair the 02-08 Explorer without removing the dash, and replacing the door with metal that will outlast the Explorer. Check HeaterTreater.net.