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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > DIY Guides > E90, E92 Final Drive (Differential) Oil Change Tips



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E90, E92 Final Drive (Differential) Oil Change Tips
Published by NoTempoLimitN54
01-21-2013
E90, E92 Final Drive (Differential) Oil Change Tips

***Right now this is going to be a "place-holder" as I gather up all the info and some more photos. I just wanted to get this started to make sure that it gets done, as I'm a busy guy. So keep checking in as I will be making updates until this becomes a solid DIY. More photos, part numbers and sources will be added. And please post if you have any information or comments.***

My 2009 335i E92 is just past 50k miles. Last week I tried to change my final drive (differential) oil. After a discouraging hour under my car where I only managed to get an oil sample (small Blackstone bottle) and probably about 0.25 L of the old oil out, I filled the diff with fresh oil and put in the plug.

Later as I was e-mailing someone for advice about this, I realized where I had gone wrong. Take a look at the photos of the E9x final drive (FD). As we all know there is no drain plug (thanks BMW!) But take a look at the fill plug. The threaded hole points UP towards the top of the FD housing. But the oil is all down in the bottom "sump".

The plastic hose of an oil extractor is designed to go through the dipstick of an engine, and is rigid. But what you need is to turn a sharp angle right after the fill hole.

Look at the photo with the FD cover off, showing the differential. There is plenty of space to the right of the ring gear, and that's the side that the fill hole is on. But you need to turn sharply down before hitting the differential body and suck the oil from the "sump".

Solution: Make an angled suction tube and attach it to the oil extractor tube. I made mine from 0.25 in copper tubing. A larger piece of vinyl tubing connects the copper suction tube to the oil extractor tube. I used some silicone electrical tape to increase the diameter of the oil extractor tube so it would be an air-tight fit. Zip ties hold it together. Not only does it go into the oil fill hole, and reach down to the bottom of the sump, but it holds itself in place, allowing you to go back to your oil extractor to pump a vacuum.

It worked perfectly! It did not take long to extract about 1.25 qt of old differential lube.

Now it's time to put the new gear oil in. BMW factory fill is Castrol SAF-XO. This is only available in the U.S. from the dealer in bulk. You have to bring your own bottle and they sell it in 0.5 L quantities for almost $20.- (that's $40.-/L). There is also a Land Rover equivalent, but that's $30.-/qt.

There is nothing so special about SAF-XO to pay $40.-/L. So I am using Motul Gear 300. It has exactly the same viscosity at 100║ C as SAF-XO, but has a higher viscosity index. It has a lower viscosity at 40║ C than SAF-XO, meaning more "flow" and slightly less power loss in the Final Drive. Cost is about $19.-/L for Gear 300.

I tried to use the built-in spout and squeeze the oil into the diff. After spending some time squeezing the life out of a Gear 300 bottle, I decided to try my China Freight (OK Harbor Freight) fluid transfer pump. I thought the hoses it came with were too long and I did not like the fact that they were not transparent.

Well it turned out the vinyl tubing I bought fit right into the red hose that came with the pump. I cut one red hose just long enough to reach the bottom of the 1L bottle and cut a short piece to adapt the vinyl tubing to the transfer pump.

MUCH easier. And these pumps are so cheap you can just have one for each type of oil and keep it sealed up in a zip-lock bag. No need to flush it out to get the old oil out.

OKů all for now, I'll be refining this DIY as time allows and adding details, part numbers, sources, etc.

NoTempoLimitN54
__________________

2009 335i 6MT (E92/N54), Black Sapphire / Shadowline (Individual 760) / Black Dakota Leather, ZSP, ZCW, 6FL, PDC, no Nav/iDrive, 19 x 8.5 / 19 x 9.5 VMR VB3 in Hyper Black, Pilot Super Sport 235/35 fr 265/30 rr, M3 control arms + tension links (fr)
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