Changing differential oil on a 310s - BMW Open

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Aerial_stu
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Changing differential oil on a 310s - BMW Open

I've attempted my first oil change on my BMW open diff.

if you want to avoid the same mistakes I made, you can see how I did it here. 

YouTube linky

Graham Hutton
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Great video as always, many thanks for sharing. I originally filled my diff in the same way as you when I built the car but I think this time I'm going to try sucking it out with a big syringe and refilling the same way. Once I rinsed the diff oil out of my hair I'll let you know how I got on.......

Exeter, Orange 310R

ScottR400D
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Well, I guess you know the mistakes you made now? No need to remove any of the boot floor, with car on stands. Remove the drain/fill plug, suck out the oil with a Pela extractor, pump new oil in with a Sealy 6804 or similar, put plug back in. Job done!!!

If you replace the standard plug with a magnetic one, as many of us have done, you just need a ring spanner to remove it.

Did you discover what 'No Oil' means? As I think you surmised, it's put on when the diff leaves the factory with no oil in it!

L7C
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L7C
StevehS3
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My BMW diff took about 1.2L to the fill level. Is in fact 0.8L the correct amount? 

Aerial_stu
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You're correct, my book says 1.2 L

I was asking about oil on a FB forum and the conclusion there was that new editions of the manual says 0.8L due to the seals leaking.  Mine don't leak, but I've put in less than the 1.2.  Probably 0.9 - 1 L will be in mine.

check for your own car.

Regards,

Stuart

Aerial_stu
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Hi Scott, yes, sounds like a sensible approach!

Regards,

Stuart

StevehS3
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#6 Thank you. Mine has not leaked with 1.2L but having searched there is this explanation here https://www.caterhamlotus7.club/forum/techtalk/bmw-differential-have-you-had-oil-leaks-output-seals for the 0.8L fill. 
 

"I have been doing some research after comment about the fill quantity recommended could be 800ml.

The Diff is mounted in BMWs the other way up ie with the filler plug pointing down. So the installation in the Seven makes the BMW Diff upside down?!

This means the fill level is altered. Installed in a BMW the oil level when it dribbles out of the filler is JUST BELOW the output seal level & equates to about 800-900 ml. In a Seven the fill level is above or at the output seal level. Caterham quotes that the fill is 1.1-1.2 litres.

So are we overfilling our BMW Diffs? And of course some of us are then unlucky to get a leak." 

ScottR400D
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It's not mounted upside down. The filler in the Caterham backplate is in the same place as on the BMW backplate. 

Most don't leak with 1.2L and the best explanation I've seen for the ones that do is that the drive shaft seals aren't fitted in the optimum position.  However, never having had the issue, I haven't looked into it that closely. 

BMW apparently used to say 1.1- 1.2L for the 168 diff but changed that around 2011 to 0.8/9L. 
 

 

L7C
StevehS3
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#9 Thank you. I have 0.8L left over from changing the diff. I think I will do an oil change leaving about 0.9 in the diff as Aerial Stu did. 

Geoff Brown
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Going through the boot floor is just additional faff & IMO more of a PITA. Whatever way there will be some mess!

High on axle stands & access to the filler/drain is remarkably easy. I am sure that this very subject was discussed in another thread?

I believe that 0.8L is the new suggested level for BMW diffs. I usually put 1L for ease of measurement purposes as there could be some unintentional spillage. Oh the whiff of GL5!