525i whining in rear

[ctroxtell]

My 5spd 525i has 282k miles, recently on a road trip I noticed there was an annoying thing sound coming ng from the rear of the car. Jacked the car up put it in gear and it seems like it's coming from the differential.

Once you get about 25-30mph you can hear the whining and it gets louder with the speed. It whines in gear, out of gear, clutch in and out. What can I do about it?

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[squirrelhill]

As a starting point, you may want to check and perhaps change the diff fluid. There are plenty of DIYs out there and it is a pretty straightforward job. Easier with the car on a lift, but can be done in the garage on jack stands.

[ctroxtell]

Any recommendations on diff fluid?

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[kojo96]

If you have LSD, you must use appropriate fluids, otherwise it'll damage the clutches. I use Castrol Syntrax LSD 75W-90

[ctroxtell]

Pretty sure it's not a LSD I can see the tag on it and I can see 3 23 90 but no S.

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[cirrusblau]

The "S" is before the ratio of the diff which is usually 3.xx. Alternatively if you have the rear on jack stands spin one of the wheels freely. If the wheel on the other side spin the same direction as the one you've spun, you've got an LSD, otherwise it while spin in the opposite direction.

I agree, check you fluid levels. Open the fill plug, if nothing drips out, you're low on fluid. Check also for leaks.

[kojo96]

And always always loosen the fill before you drain the diff.