friction modifiers
 

I plan on changing my differential fluid in E420 non-limited slip. It seems like all gear oils contain friction modifiers which are recommended for limited slip differentials. The only gear oil I can find that doesn't contain them is redline 75-90NS. Is it detrimental to the differential to run gear oil which contain the modifiers (e.g. mobil 1) in a non-slip differential?

No.

Duke

You sound like Larry Bible. :D
A few threads down ( see " jackpoints " ).

It's easy when someone asks a simple question, providing necessary background, that can be answered with a simple "yes" or "no". ;)

Duke

So the next question that comes up. Is it better to use gear oil that doesn't contain friction modifiers for a non-slip differential?

It doesn't make any difference. The friction modifier is there to prevent clutch chatter. With of without, a proper GL-5 gear oil has the necessary EP additives that are needed for the hypoid gear set.

My recommendation is to use a mineral oil based 80W-90 GL-5 that you should be able to procure at any auto parts store. Eventhough the label may say "suitable for limited slip differentials" most DO NOT have friction modifier. One exception is Redline 75W-90, which does, but as you said 75W-90 NS does not.

Duke