Q: how do i check and change the rear differential fluid? on 2000 Ford Explorer

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with in the past month i would hear a noise coming from the rear end when i would press the gas and i was told it might be that the differential fluid had ran low or broke down but i have no idea on how to change the fluid or check it?
(1) Answer
The rear differential has a fill plug on it, and fluid can be filled to the hole. Replacing the fluid requires removing all the bolts on the differential cover and removing that cover, allowing all the oil to come out. Then you clean the surfaces and use new sealant to reinstall the cover. Finally, refill the fluid - using a friction modifier additive if your rear differential is a locking one.

Addressing your specific concern - the ring and pinion may be making some noise in your rear end. Noise concerns are generally not solved by adding or changing the fluid, unfortunately. Noise typically indicates damaging wear is already done. A good inspection of the rear differential with the rear cover off is in order - it can be checked for gear lash and physical condition.

Good luck and Happy Thanksgiving!