How often do you change the differential fluid?

Bought my '15 DCSB OR back in 2020 with 76k on the clock. No record of previous service, and based on what I saw come out I'd lean towards it being factory fluids but no way to tell for sure. Using Amsoil Severe Gear 75w90 going forward because that's what I like, YMMV.

Changed all diffs at 80k and sent samples to Blackstone. Front diff oil looked TERRIBLE coming out but test was A-OK. Rear diff had elevated metals but they said it's likely break-in wear. Transfer case looked brand new but was the worst test results of the bunch with high insolubles and copper. Moral of the story: don't judge oil condition by how it looks in all cases. Links here if you want to see the test results for yourself: [#55][#56][#72][#135]

I'm about to dump them again & send in new samples. I'd expect the tests to come back much better this time unless something is already gone wrong - which I highly doubt as it functions perfectly.

Tests cost $30 but my time & peace of mind are worth it. Frankly I spend more on other dumb mods & toys, oil tests are what I consider cheap insurance for expensive driveline parts.

 

Hahahahhahaa

 

50k miles