I change diff oil after a few years. It is black, and the stuff I put in is a nice clear blue color. It is not getting combustion blowby as in engine oil. BTW is rear drive, not limited slip. And is not one of those V8 cars with stage 3 tune, 500 kW on the dyno, so shouldn't be overheating.
why does diff oil turn black?
Feb 24, 2023
1 Replies
It's all metal oxides and sulfides building up in solution. Feel those gears after 200,000 miles and notice how sharp the tips are and thin the teeth are? The metal that used to be on there is now in solution in the fluid.
--scott
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