sorry guys, the Mother's day weekend was a bit busy with the family...

In continuos search of this forum for more info in reference to the rear differential leak I have come across this post from 2009 where the differential is said to have Limited Slip Differential (LSD) and therefore calling for a much heavier fluid with LSD additives... This statement was not really challenged in the thread, so the question about the diff fluid is back...

What is the correct fluid for a 2006 e53 4.8is rear differential (110K miles)?

Synthetic gear oil 75W-90 or 75W-140 (Castrol XAF-XJ)?

http://www.xoutpost.com/603577-post27.html

Fariz that is the first time I am hearing about the front/rear units being limited slip units.

After a couple years on here I have noticed no difference in front/rear differential fill recommendations other than using a good 75w-90 synthetic.

Only driveline fluid difference between all runs of E53 should be whether you have NV125 transfer case with ATF or the ATC500 transfer case with Xdrive fluid, and obviously the transmission fluid difference whether AT or MT.

Did Realoem say anything on this?

I was under impression that the fluid is to be 75/90 and not 75/140, but I will call the dealer and ask them directly. The RealOEM is silent in this reference - in the fluids section there is no listing for this fluid - I guess the "lifetime-ness" plays its role, even though I thought that leaked fluid had to be replaced (not as preventative flush but as a repair) with some "part number"...

I will post with the answer from a dealer...


Another question - JCL mentioned some collapsible one time use spacer - which part is it on the diagram and should i be getting a replacement spacer (since the one installed is already used that single time)?

A quick search elsewhere confirmed the original SAF-XO is for 'non limited slip' diffs, with a different BMW coding for the few bimmer LS diffs [Ms, it appears, mostly]. a Castrol reference indicates that this is 75w90 weight gear oil. This conforms to Bav Auto [one example]'s recommendation of RedLine 'non-LS' 75w90 synthetic gear oil in our vehicles, which is what I have [with the Lubro-Moly antifriction additive] - though RedLine 75w90 can be had 'with' LS additive, too. The product description language on the xdrive system is a bit confusing, but the short answer is that E53s do not utilize a 'limited slip' differential of the type [clutches] that require the LS additive. FWIW, I added an Eaton 'geared' LS differential to the rear end on my first Ford 7.3L diesel truck after its 'original' LS 3.73 diff died. The original Ford LS required 75w140 syn oil with LS additives; the Eaton 'geared', not 'clutched,' LS did not require the LS additive. That said, a 'non-LS' can work fine with either. I'm from the 'don't use it if it isn't called for' school, and have NO LS additive in my pumpkins ...

BMW of Sterling just told me - 75w140

I am going to call couple other places, for further verification...

Well I have 75w-90 in mine, and 75w-90 came out of it and was recommended by my indy and my local shop. ECS also sells 75w-90 in their differential fluids section.

http://www.xoutpost.com/bmw-sav-foru...ial-fluid.html

I'd only go for 75w-140 if you lived in like friggin Mexico or something or do heavy towing/hauling for a living.

Get the Lubro Moly 75w-90 GL-5 oil for both diffs (non-limited slip), and be happy. To be honest I don't trust the dealer much when it comes to asking questions for a 10 year old X5, they don't seem to care enough to research proper information...

Chill, RB, chill! OP, believe who you want, check all you want, but the original fill is 75w90 synthetic, no LS additive. google bmw SAF-XO and you will see - read the Castrol site describing it, if you like. As for 75w140 - Ford changed their recs for the big Sterling 10.5" rear diffs on their diesel trucks to this weight because heavy haulers [and high torque from the 7.3L diesels hauling 10k+ trailers ....] were overheating other fluids. Not an issue in this application. For newer bimmers, or 3 series used on the track, sure, maybe. :)

Oh, I do think it is the 75/90, and i don't trust the dealers - the BMW of Fairfax told me 15w/60, I did not even write this in the post, that is how ridiculous that info was...

I found the SAF-XO part number 83 22 9 407 768 in 75w/90 weight that comes up in the motorcycles in the RealOEM and matches up to the LubroMoly oil I mentioned earlier...

I am leaning 95% towards that particular weight and brand but I was taken aback by the LS info for the x-drive and the 75w/140 statements...

You got to be kidding me about BMW Fairfax :rofl: Do they even know what a differential is?

Our differentials front/rear are definitely non-LS units for sure.

Here is your Lubro Moly gear oil should you wish to use it in your diffs!

Search Lubro Moly - 2048 - Manual Transmission / Differential Fluid 75w90 - 1 Liter - ES#258729

http://c1552172.r72.cf0.rackcdn.com/325581_x600.jpg

Yeap, this is the one I am getting...