I think what you meant to say is diff fluid with LS additive is ok for either LSD or non-LSD equipped vehicles.

BMW diffs require the additive or you'll wear the clutch packs out in no time (as well as hate life while the diff chatters, etc.).

Dan at diffsonline.com is the guy to go to for BMW diffs. He built my race car diff up for me (back in the day).

You would think the xdrive descriptive data would just tell you its an 'open' differential [i.e., not a limited slip of any kind] with the magic in the transfer case. I'm no engineer, but I can usually comprehend well-written descriptions of mechanical devices; however, the bmw xdrive stuff gives me a headache. I'm sure the Liqui Moly version will work fine.

That depends on whether you want to pull the diff internals, inspect them, reassemble, pull the rear axle half shafts and then reset the preload on the pinion....OR if you just want to replace the pinion seal. Are you going for a tear down or a seal replacement? The whole reason to mark the location of the nut is so you don't have to replace the collapsible spacer.

You are greatly overthinking this. I thought your tech was going to do it anyway? Replace the seal. Return the retainer nut to the same position. Refill with 75w-90 with no LS additive, because you don't have clutch packs in your diffs. Drive the sucker. Pretty simple.

Fixed it for you.

It is an open differential, but not an open system. Limited slip is provided by wheel sped sensors in combination with a computer, the ABS module, and wheel brakes.

The transfer case for x drive variants of the E53 handles front/rear, while wheel brakes handle side to side.

Good man, JCL, thanks. I'm with you on keeping this simple, if you can; I spend more $$ than I wanted having a 10.5" Sterling 3.73 Ford rear diff rebuilt, with the replacement, geared differential to replace the worn out clutch packs in the original Ford. And yes, I understand [generally] how the various components work in the Xdrive system - of which the differentials are possibly the most straightforward.

Until you get to DPC, which uses torque vectoring. Came out on the X6 IIRC. BMW uses an electric motor to spin a planetary incorporated into the diff and direct power left or right. On large track type tractors we called it differential steering. Cat used a reversible hydraulic motor instead of an electric motor. Instead of braking one track you could do full power turns. Worked very well.

you are right, I am overthinking - since i can't do the job myself, i have to delegate the work to a mechanic, and while he has proven himself a worthy mechanic, i still worry a lot, especially after talking to "professionals" at dealerships... this work involves gears, tolerances, hydraulics - things that i am not comfortable with... it is not like sticking a little camera into a French Ambassador's bedroom... not that we do or would do something like that!!!:nanana:

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yes. Typing lagged brain thoughts... Thanks! :thumbup:

Thank you Jeff for doing that as I didn't want misinformation coming about that we had LSD units in our E53's. Would be more like the ultimate off-road and hauling machine instead of sport activity vehicle if BMW really equipped all E53's with limited slip front and rear diffs (and I'm sure would have added handsomely to the cost as well!)

75w-90 non-limited slip synthetic gear oil front and rear for all E53, sticky that info.