Front dif oil - 450i

[DaveTJ321]

My front differential looks like it's leaked because there's wet dirt stuck around the front/bottom seam.  I'm confused about how high the level should be inside.  On the top of the differential above the fill plug there's a stamp that says "oil level."   On the bottom of the differential below the fill plug there's also a stamp that says "oil level."  Also, if I was to top it off if needed, I know SAE 80 is recommended.  I've got a bottle of limited slip oil.  Is that ok with the locker?

[airshot]

I use full synthetic 75-140 wt diff lube and fill to the bottom of the fill hole. Make sure the bolts are tight holding the 2 halves together.

[DaveTJ321]

Thanks, but if I just want to top off what's already in there?

[airshot]

If you havent already done so it is recomended to drain and refill the diffs once per year.  Never know when some water might eep in there and also helps to flush small metal particles out that could eat thru seal over time. Mine get drained and filled each spring and mabey even again in the fall if I have rode hard or thru lots of water over the summer.  Cheap insurance!!

[DaveTJ321]

I just changed the front diff oil to the full synthetic 75-140 like recommended.  It didn't seem like enough drained out probably due to the leak I mentioned before.  Also, on the drain plug there were tiny metal pieces.  After it was done draining, I sprayed it out with brake cleaner and refilled the oil.  Took it for a test drive and shifted to 4wd.  The shift sounds louder than it had before.  Any idea why?  I know the metal in the oil probably wasn't a good thing.  I've only got 200 miles on it but it was my first diff oil change.

[airshot]

Change it again, ccheck again for metal particles and remove them if needed. You need to be sure all that brake cleaner is out of there!  You can go even heavier on the diff oil if you go full synthetic. I use 75-140 full synthetic and the factory told me that was even better than straight 90 gear oil.  Made my diff quieter as well.

[mstparker]

Change it again, ccheck again for metal particles and remove them if needed. You need to be sure all that brake cleaner is out of there!  You can go even heavier on the diff oil if you go full synthetic. I use 75-140 full synthetic and the factory told me that was even better than straight 90 gear oil.  Made my diff quieter as well.

I copied airshot on the lubricants. Even filled the diffs till the lube ran out the fill hole.