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How To Change Your Diff Oil

65K views 113 replies 40 participants last post by  reynolds.laurie89 
#1 ·
As requested by a couple of people....

This is a guide for changing your differential oil, this relates directly to a M135i, but I'm sure it would be a very similar procedure for any BMW. I did mine laying behind my car in the street in a few minutes.

Before you start, you'll need a litre of GL5 diff oil; a pair of rubber gloves (unless you prefer the spare bed), a 14mm Allen Key or similar; something to catch the old oil in; and tool/method for refilling the diff, here's my kit:

photo 2 20_zpsyvqxjttq.JPG


(I'm using 75w140 LSD oil for my clutch-type Drexler LSD, but) 99.9% of people with their open diffs will need a 75w90 GL5 (including Quaifes). Notice the Oil Gun, basically a big syringe, which makes things very easy. About £5 on fleaBay.

I'm fitting a Magnetic 'Dimple' diff plug today, M22x1.5mm, 9mm thread. . This is particularly important if you fit a Quaife, as they're known to create quite a bit of metal dwarf inside when running in from new.

Diff 2.jpg


Start by popping your gloves on (old gear oil is nasty stinky stuff - old clothes are also recommended). Position a tray / plastic sheet under the diff ( to save your driveway - although you really won't drop much ) then remove the plug. Next, suck the old oil out using the suction gun. After only 20k, mine was pitch black and a bit thin. It's doubtful you'll get 100% of the old oil out, but 900ml is easy enough to extract in 4 or 5 pulls. Try the tube in a few different locations to maximise the extraction.

Diff 3.jpg


Bear cleanliness in mind, you don't want to knock any crud inside at any stage, or you could do more harm than good.

Refill the diff with roughly 1 litre of nice new golden oil. :) I simply sucked it out of the bottle, and blew it into the fill hole. When it's full, it will just start trickling out again.

Refit your plug and torque to 60Nm / 44 lbft, done!
 
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#3 ·
Cheers Robbles.

I'm doing this LSD every 20k, but for a standard open diff I usually leave it somewhere between 33k - 50k.

Basic routine maintenance, far cheaper and easier than £1000 for a new diff! Especially important if you have a car with a known weak diff, like the 2004 - 2006 118d.
 
#5 ·
Great post, I'm not confident enough to do it myself but it is number 1 on my list to do

Sent from my GT-I9505 using Tapatalk
 
#7 ·
:? The oil sucks out pretty easily even when cold? It's not like an engine where you want it to drain out of all the fine galleries?

I could understand giving it a high speed run directly before hand (to stir all the crap up from the bottom into suspension), but I'm not convinced working on a hot diff is better / easier?
 
#8 ·
marco_polo said:
:? The oil sucks out pretty easily even when cold? It's not like an engine where you want it to drain out of all the fine galleries?

I could understand giving it a high speed run directly before hand (to stir all the crap up from the bottom into suspension), but I'm not convinced working on a hot diff is better / easier?
Not as hot as an engine or sump when doing an oil change ?
Each to their own I suppose but as you say and I agree the sediment needs mixed with the oil if the car has stood for a while as there is no separate drain plug. It would be even better if the diff could be flushed completely as they do with some of the Hondas, Three times in total to clear all the debris out.
 
#19 ·
Visually you can't tell easily, I doubt many people would drop £2k on a diff and then not try to use it as a selling point though. It's a huge plus for any BMW.

If they had fitted a Quaife (the most likely LSD in Britain) it might not be relevant, to the oil anyway? There aren't any clutches inside a Quaife which need an oil with the friction modifiers in, they work via interlocking helical gears instead.
 
#21 ·
Sorry to bump..

Is it worth fitting a magnetic diff plug on my '55 118d?

On 112k miles, no record of an diff oil change either. Currently all is totally fine and no noises or anything, but changing the oil in it this weekend to preserve. Got the oil and the drainer / refiller, just wondering if its worth it?

Have heard my 1er (being a 55 plate 11:cool2: is prime for having a weak diff? It has a stage 1 map on it too so is doing about 35/40(ish) BHP more over standard, plus torque etc.
 
#24 ·
Used the same stuff on the E90 320d and the non LSD Syntrax stuff on E87 120d did it about 75K miles on the clock. Needed over 2 litres each time. Tied it in with a coolant and ATF/sleeve & sump change. The diff oil think it's a lifetime fill which equates to about 100K miles. So best before then...
 
#25 ·
Nice write up Marco. Ordered my oil and magno-plug ready for a nice bit of TLC soon! Cheers
 
#26 ·
Planning on doing an oil change on my manual transmission and diff when I do a 12 month engine oil change next month on my M135i. Does anybody know the torque specs for the diff plug? The housing is alu and I don't want to go stripping the threads. I've seen some torque values of 60Nm quoted on Bimmerfest but that was for an E90 diff.
 
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