Should i replace liquid in the rearend i got from junk yard before i install?

Question

im replacing a rearend in my bronco and i got a new one from a junk yard. im sure it has gear oil in it, should i just trash whats in there and start fresh? is it fine just to use the old stuff?

Answer 1

I say change it anyway. There's no way to be sure how old that gear oil is. Two quarts of gear oil should cost about $10-$15, and it's easy to do. Better safe than sorry!  

Answer 2

By all means, change the oil. It's cheap insurance that there is no water inside. Be sure to check if it is a posi unit, because most of them take an additive for antifoaming. Also, gives you a chance to see if it has any damage to other parts, hopefully not.

Answer 3

I would look to see that it's full and then install it and see if it works and if it does then change the oil.