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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > Differential oil



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      07-18-2012, 07:23 AM   #1
kavadarci
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Differential oil

Hi,

Just wondering that instead of using a pump and getting the oil via the diff bolt, why can I not remove the differential back cover so I am sure all the oil is out?
Any reason for not doing this (except the mess)?

Thank you.
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      07-18-2012, 07:43 AM   #2
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I wouldnt see a problem either, maybe youd have to replace a gasket if you did so.
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      07-18-2012, 08:13 AM   #3
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Quote:
Originally Posted by kavadarci View Post
Hi,

Just wondering that instead of using a pump and getting the oil via the diff bolt, why can I not remove the differential back cover so I am sure all the oil is out?
Any reason for not doing this (except the mess)?

Thank you.
I thought about doing this too, but decided just to use a pump.

I don't believe there's any reason you can't do it, but you substantially increase the risk of "collateral damage" from a routine maintenance service. Do you know the precise torque specs? Is there a specific torque order? Any one-time fasteners (stretch bolts or whatever) used? What if something does go wrong? I'd recommend having a gasket and at least one new bolt on hand in case something goes wrong.

This is another case where overmaintaining a car actually makes things easier. If a fluid is changed "early" it doesn't matter if you only get 80-90% of it out because it's still in good shape. If you push your intervals as far as you can then you feel more compelled to get every last drop of filthy, expired fluid out of whatever it is you're working on.

I think I saw comments from Mike Miller quoted somewhere indicating that for the first time the longevity of a BMW MT driveline "remains to be seen" with the E90. For decades they've been overbuilt and you can have a high degree of confidence that they'll last forever. Now they made the gear rings smaller, cheapened the design of some key bearings etc... This tells me that high quality, aggressive fluid changes are more important than ever.

Let us know how it goes and if you run into anything interesting. Having no drain bolt is really annoying and frustrating to an over-maintaining DIYer like myself.
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      07-18-2012, 11:04 AM   #4
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Quote:
Originally Posted by Surly73 View Post
I thought about doing this too, but decided just to use a pump.

I don't believe there's any reason you can't do it, but you substantially increase the risk of "collateral damage" from a routine maintenance service. Do you know the precise torque specs? Is there a specific torque order? Any one-time fasteners (stretch bolts or whatever) used? What if something does go wrong? I'd recommend having a gasket and at least one new bolt on hand in case something goes wrong.

This is another case where overmaintaining a car actually makes things easier. If a fluid is changed "early" it doesn't matter if you only get 80-90% of it out because it's still in good shape. If you push your intervals as far as you can then you feel more compelled to get every last drop of filthy, expired fluid out of whatever it is you're working on.

I think I saw comments from Mike Miller quoted somewhere indicating that for the first time the longevity of a BMW MT driveline "remains to be seen" with the E90. For decades they've been overbuilt and you can have a high degree of confidence that they'll last forever. Now they made the gear rings smaller, cheapened the design of some key bearings etc... This tells me that high quality, aggressive fluid changes are more important than ever.

Let us know how it goes and if you run into anything interesting. Having no drain bolt is really annoying and frustrating to an over-maintaining DIYer like myself.
Thank you for the response.
I'll let you know how it goes.
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      07-18-2012, 09:46 PM   #5
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You don't want to try it. There is a big-ass bushing attached to the rear diff cover. You have to remove the bushing bolt and the bushing and drop the diff to get the cover off. It's NOT like pulling the diff cover off of a pickup truck. My advice is use a pump. Then you have to replace the diff cover gasket, but it's cheap, under 2 bucks.
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      07-18-2012, 10:03 PM   #6
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i will take your advise. which one is the diff cover gasket? in the diy doesn't have any gaskets. thank you.
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      07-19-2012, 06:21 AM   #7
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Originally Posted by kavadarci View Post
i will take your advise. which one is the diff cover gasket? in the diy doesn't have any gaskets. thank you.
I did my fluid change a month or two ago. I believe that none of my diff or MT plugs required a gasket/sealing ring/washer. IIRC, my diff plug had an integrated O-ring seal. On my E39 you had to change the gaskets although the plug was eventually "updated" to be like the one on my E90.

I have a 2007 328i 6MT sedan, if it makes any difference.
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      07-19-2012, 11:08 AM   #8
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I measured how much I pulled out with a regular pump, and I could see that I wasn't getting it all - I was at well under a qt, and changed to a vacuum brake bleeder with a thinner more flexible hose that got to the bottom of the diff. When I filled, it took 1.2 qt., so I'm confident that I got 95+% of the fluid.

I had posted the comments by Mike Miller saying the diff is now under-built, and that is critical to change the fluid on a more frequent basis. He recommends Redline.

Quote:
.. E90 non-M diffs too new for longevity predictions, but not looking good... diffs have gotten smaller, pinion gear now very small, oil capacity reduced, and strong tapered roller bearings were changed to regular ball bearings... diff. rebuilder thinks fluid changes is the best bet for maintenance, but is also suspicious of the plastic bearing cage.
Further, he recommends 1/4" plastic/vinyl tubing to reach the bottom of the differential. As most oil extractors come with 3/8" plastic tubing, which is too big, you need a reducer and quarter-inch tubing, or as I did, use a vacuum brake bleeder with 1/4" tubing.

Last edited by AlanAZ; 07-19-2012 at 04:56 PM.
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      07-19-2012, 07:29 PM   #9
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Thank you.
i was thinking of redline or purple blue but found the oem oil to be the same price so i bought oem. it can't be worst then the one in it right now.
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