Hi guys I am just wondering if there is anyway I can substitute gear oil for something like motor oil or ATF fluid??

I have a 2002 Chevy Blazer 2DR 4WD thanks !

 

You could pour water in there if you were so inclined...but don't expect it to last too long that way...

To less sarcastically answer... No, you should not use motor oil or ATF where gear oil is required. Neither of the two have the shear properties required to protect the components inside the differential. It isn't like 80w90 GL-5 gear oil is all that expensive or readily available at almost any store that carries oils in general.

 

Agreed, the $15(exaggerated) you'd save by putting anything else in the differential would cost you hundreds later.