Rear Diff fluid change DIY

[TTGator]

Thanks for the info! I combined this with stuff from a couple other sources I found while researching this and took it one step further and made a DIY video tutorial.

[knightarmor]

Finally got around to doing this today. Can also confirm it's approx. 1L of fluid, although I did need the second bottle cause my pump sucks and couldn't get all of the fluid out of the first bottle.

[TTGator]

Originally Posted by knightarmor

Finally got around to doing this today. Can also confirm it's approx. 1L of fluid, although I did need the second bottle cause my pump sucks and couldn't get all of the fluid out of the first bottle.

I hear you! I almost put the rest in a different container but then it started overflowing like it was supposed to.

[m20e3087]

For the transmission flush do I need to change the fill and drain plugs?

[TTGator]

Originally Posted by m20e3087

For the transmission flush do I need to change the fill and drain plugs?

Yes, I mentioned that in the video

[TTGator]

Originally Posted by RoadRunner///M

I believe you only need 1 litre of fluid, not 1.5. The kits that ECS sell are 2 x 500ml bottles

https://www.ecstuning.com/BMW-F80-M3...ce/Drivetrain/

Correct

[TTGator]

Originally Posted by RoadRunner///M

When was ECS selling the incorrect oil? I bought some from ECS months ago and its been sitting on my to do list. It is Castrol Syntrax Limited Slip 75W140, which seems to be formally SAF-XJ

I just saw someone in the forum thread where I got a lot of the info saying they were selling the +FM version for the F8x kits. Not sure how long ago it was though.

[overlook637]

Royal Purple and Mobil1 doesn't have a recommend gear oil.

[WTF82]

Just want to say thank you for posting this. I'm going to do this soon. The stealership wanted $600 for a diff fluid change. I almost gave in because I thought it would be easier for them to do it, but the service tech said it's $300 just for the fluid itself and after pressing X to doubt, I declined. Just picked up everything I need from ECS for less than $100.

[Samf82m4]

Where did you get the torque spec for this? BMWs service manual for the F80/F82 indicates 45NM.

[knightarmor]

Would also be curious to know which one is correct?
I just did this again, torqued to 44ft lbs same as the last time I did it!

[Samf82m4]

Originally Posted by knightarmor

Would also be curious to know which one is correct?
I just did this again, torqued to 44ft lbs same as the last time I did it!

See post #8 on the thread I started. It's definitely not 60nm. What's funny is that you can tell everyone on youtube copied this thread. Scares me to trust any torque specs I see in videos now lol.

Sounds like the old newtis pages weren't very reliable besides instructional steps.

[knightarmor]

Originally Posted by Samf82m4

See post #8 on the thread I started. It's definitely not 60nm. What's funny is that you can tell everyone on youtube copied this thread. Scares me to trust any torque specs I see in videos now lol.

Sounds like the old newtis pages weren't very reliable besides instructional steps.

Great, thanks for the follow-up and clarification. I will update my notes accordingly!

[theweebabySeamus]

Anybody that's done this, does it need to be jacked up or would a couple of 2x8's provide clearance? I want to do it this weekend but don't have jack pads yet.

[marauder1]

Originally Posted by theweebabySeamus

Anybody that's done this, does it need to be jacked up or would a couple of 2x8's provide clearance? I want to do it this weekend but don't have jack pads yet.

Really just need enough room to get under there and to be able to transfer the fluid. A single 2x4 might not get it high enough.
You don't really need jack pads. I jack it up all the time without them.

[Stronie]

Great write up, Fluid changes upcoming.

[D0NVT]

Hey guys, I'm sorry for off top, but what kind of oil is better to use in S2T4 m-active rear differential such as M340i or 330D G20?
TIS says it's Hypoid Axle Oil G4 P/N:3 22 2 447 362;
Redline official site recommends 75w85 LS oil.
But is it better to increase viscosity to 75w90 LS or 75w140 LS?

[alexk780]

Sorry to revive an old thread here. But am I reading this correctly, the drain bolt is torqued to 45nm but the fill bolt is torqued to 60nm. Can someone confirm this, I am doing this job this weekend and would appreciate the input here.

[Pete.J]

Wrong fluid for the electromechanical LSD differential, it will work, and BMW has it listed as right oil. But that fluid has FM boosters in it (Friction Modifiers), to reduce diff chattering sound when cold. This isn't something that the F8x platform suffers from, this is mainly for the E82 1M, E9x M3, and E6x M5 and M6, as they had that ancient GKN Visco-Lok unit that that made loud noises when performing sharp turns at low speeds. In order to quieten the noisy diffs, BMW revised the fluid, and added FM (Friction Modifiers). Friction Modifiers make the fluid more slippery, and hence quieter operation, softer, smoother, and slower LSD lockup, on the expense of accelerated clutch-pack wear.

The electromechanical LSD in the F8x locks on demand, and you certainly don't need FM there to smoothen or slow down the lockup in an attempt to quieten the diff, GHAS module controls that for you. The presence of FM will only wear out the clutch pack quicker over the course of 80,000km worth of street driving or so. Worse if driven hard or tracked.

This link below should be the correct fluid for the F8x diff, same as SAF-XJ you got, same viscosity, and same everything (both made by Castrol anyway), but the one below doesn't have additional Friction Modifiers added to it, as BMW requested to be added to quieten those old diffs on previous gen ///M cars.

Many dealers around the world had been using this OEM Castrol fluid for the F8x from day 1, instead of BMW's SAF-XJ fluid with the additional FM. It's also the factory fill, the SAF-XJ is probably listed in the parts catalogue to streamline supply chain (i.e. one diff fluid to suit all ///M cars, since they'll all work fine anyway, customers won't notice any downsides, and won't complain).

This is what should be used on F8x, for faster harder LSD lockup, and longest possible life out of the clutch pack (it's certified by BMW, and also what Mercedes recommends on their electromechanical LSD for their AMG cars):

https://www.fcpeuro.com/products/syn...castrol-1543c9