differential fluid change
 

I would like to know when the differential fluid should be changed. My car is soon going to have 200k miles and it has never been changed. It is one of the few things that perhaps has been overlooked. If it needs to be changed what gear oil should I use, how much of it am I going to need and how do I go about changing it, thanks.

if it isn't leaking, hypoid gear oils last basically forever in a differential.

it uses a couple pints, I believe its SAE 80W90 Hypoid or similar gear oil. there's a drain plug and a fill plug on the back of the differential, they strip very easily. clean off the whole back of it before you pull them so you don't get any dirt inside. you fill it right up til its overflowing out the fill hole.

It is not leaking so I guess I am OK. If it ain't broke don't fix it.

true that:
 

But if you do, always remove the fill plug first before the drain. This also applies to manual transmissions. If the fill plug won't come out, you are s.o.l.