SAE 90 vs 75W-90 Is this OK????????

[shiprek]

I am going to change the fluids in my front/rear differential and transfer case. I have looked in my manual for the proper viscosities and quantities. Question: My manual says to use SAE 90 in the front differential but I see folks seem to be using 75W-90. Is this acceptable and why? I have looked at several sites that reference using 75w-90 but none have indicated why this is OK?

Thanks for your help.

[shiprek]

Anyone? Even a guess might be helpful. Thx

[WildStyle]

75w90/80w90 ain't gonna make a bit of difference. Run what you want the differential won't care one bit.