Grinding in rear diff

[Hoffbrohaus]

I recently drained and filled my rear diff with Red Line RED57104 75W-140 NS Gear Oil just because I don't know when the PO changed it last. I fully drained it and filled it until some started coming out the fill hole. There are no leaks either.

Before I changed the oil I never heard a grinding/rubbing sound coming from the rear. Now when I turn I hear it. What did I do wrong? I think I read somewhere once you are supposed to go around in circles for a bit to coat something? I didn't do that.

[TobyB]

Limited slip diff?

Those can be sensitive to what oil goes into them...

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[Hoffbrohaus]

Yep limited slip diff. What should I put in?

[mitchlikesbikes]

redline 75w140 NS is the cheaper variant that does NOT have the necessary additive for the limited slip diff. you need to either add an LSD friction modifier or drain it and fill it with a diff oil that has the additive already in it (the more expensive redline 75w140 has it in it and works great)

without the modifier the diff will actually lock up more which is desirable in race applications. that extra lock up and bite in the diff is probably what you're experiencing.

[Hoffbrohaus]

redline 75w140 NS is the cheaper variant that does NOT have the necessary additive for the limited slip diff. you need to either add an LSD friction modifier or drain it and fill it with a diff oil that has the additive already in it (the more expensive redline 75w140 has it in it and works great)

without the modifier the diff will actually lock up more which is desirable in race applications. that extra lock up and bite in the diff is probably what you're experiencing.

Awesome thanks for the info. I will drain and refill. Wish I had caught that NS was sans additive :(