Pinion seal replacement + diff fluid question

[TexaZ3]

You may need to top off the fluid afterwards but a majority of the oil sits in the bottom of the case. The pinion bearings do not sit in oil. The pinion is lubricated when the ring gear spins and forces fluid over the limited slip carrier. If you look at the inside of a diff cover, it is curved to aid in the flow over the carrier.

Terrific - thank you!

[bigjae46]

You may need to top off the fluid afterwards but a majority of the oil sits in the bottom of the case. The pinion bearings do not sit in oil. The pinion is lubricated when the ring gear spins and forces fluid over the limited slip carrier. If you look at the inside of a diff cover, it is curved to aid in the flow over the carrier.

[TexaZ3]

I'm not really trying to save diff fluid, I'm trying to save my time and money. If the fluid will leak out when changing pinion seal, then I'll just replace it - I just don't want to spend the money and buy it, if I don't really need it. All the videos I see don't show anything leaking out, but then again, I don't know if the diff is already drained at that point.

[Slideways]

If you are trying to save and reuse the diff fluid, one way would be to thoroughly clean the drain bolt area and drain the fluid into a clean container (an empty OE diff fluid bottle or maybe a 10W60 container rinsed with brake cleaner). I was trying to think of a clean method of saving the diff fluid as well if replacing the diff cover.

[COVID-19]

Don’t know if you need to drain any but I started doing this for diff oil.

https://youtu.be/lUpOFxGtN-E

[TexaZ3]

About to replace pinion seal on my diff, and having not done it before - do I need to drain the fluid in order to change it? I just did the fluid change like, 1000 miles ago, so would hate to discard perfectly good fluid.

If I do - is the Castrol 75W-140 SAF-XJ + FM still the way to go? Or is there something better out there (aside from super overpriced OE fluid)? Thanks!