DIY: Differential Fluid Change

Did my first diff fluid change at 62K miles.. used the standard fluid from BMW ( purchased via ECStuning with new plugs ~$160). I ended up using about 2.6 bottles of fluid. Pretty easy fluid change.

I had also purchased the stubby 14MM hex from bimmertools which will avoid any complications with bolt removal. There is room above the diff to shove the bottle up there and then using the soft bottle stem, you can bend the tube into the fill hold (then squeeze the bottle)... Again, easy DIY. Took me about 30min once I had the car up

Running Royal Purple in the diff and no noises and works well.

Thanks for the DIY. The fluid change was straight forward and this is coming from someone who has never done one before!

Was anyone able to confirm the torque specs on the drain/fill plugs?

Nitro3421 wrote

Was anyone able to confirm the torque specs on the drain/fill plugs?

I have them at home from TIS and will post them when I get a chance.

Differential oil filler and drain plugs with o-ring tightening torque is 33 11 3AZ, which is 60 Nm.

ThatM3guy wrote

Did my first diff fluid change at 62K miles.. used the standard fluid from BMW ( purchased via ECStuning with new plugs ~$160). I ended up using about 2.6 bottles of fluid. Pretty easy fluid change.

I had also purchased the stubby 14MM hex from bimmertools which will avoid any complications with bolt removal. There is room above the diff to shove the bottle up there and then using the soft bottle stem, you can bend the tube into the fill hold (then squeeze the bottle)... Again, easy DIY. Took me about 30min once I had the car up

did you have your car jacked up even on 4 sides or just jacked up one side? right side?

Cbozz wrote

did you have your car jacked up even on 4 sides or just jacked up one side? right side?

I did the change myself last week. As said before, a simple DIY. Best to have the car levelled and it takes about 2.5 give and take. There is a pungent smell to the fluid that came out, and kind of a milkiness compared to the new fluid that went in.

aussiem3 wrote

I did the change myself last week. As said before, a simple DIY. Best to have the car levelled and it takes about 2.5 give and take. There is a pungent smell to the fluid that came out, and kind of a milkiness compared to the new fluid that went in.

no leaks after? did you use new bolts with gaskets?

Cbozz wrote

no leaks after? did you use new bolts with gaskets?

I did buy new bolts with embedded gaskets. But I ended up using the old ones and no leaks. If it starts to leak I have a set handy to change it quickly. It's an easy DIY. I also did the 6MT fluid at the same time and used Liqui Moly instead of BMW stuff. Slightly expensive but cannot say the difference in shifting smoothness. Good luck with your DIY

aussiem3 wrote

I did buy new bolts with embedded gaskets. But I ended up using the old ones and no leaks. If it starts to leak I have a set handy to change it quickly. It's an easy DIY. I also did the 6MT fluid at the same time and used Liqui Moly instead of BMW stuff. Slightly expensive but cannot say the difference in shifting smoothness. Good luck with your DIY

thanks a lot!!!

Great write up! Thanks

I apologize for my lack of experience here but if I believe my diff is weeping or leaking oil then will replacing the plugs be the fix or is there some other seal not mentioned in this DIY?

Part numbers would be extremely helpful. Thank you.

335m wrote

I apologize for my lack of experience here but if I believe my diff is weeping or leaking oil then will replacing the plugs be the fix or is there some other seal not mentioned in this DIY?

Part numbers would be extremely helpful. Thank you.

Depends on where it is leaking from...

realoem.com will get you the part numbers of the plugs (and anything else).

dbyrd wrote

I replaced the drain plugs - don't forget they have metal washers as well.

Can you clarify this? I just completed my differential service and all I saw was the thin green rubber gasket on the drain plug. The differential service had been done before by the dealer. Did they fail to replace some metal washers when they did the service last time?

Sean05 wrote

mine never made noise but still opted out for the friction modifier which is a lot compare to the regular..

ALSO FYI if you guys are interested on 15 bucks a bottle contact MERC... they have it without the Friction Modifier for less than half a bottle compare to BMW...

Here you go...

Good heads up. It might be an even better deal than you first thought. It's my understanding that the "limted slip" labeling on the Castrol 75w-140 (and most other brands') bottles is an indicator of a friction modifier that has been added to the differential fluid. In this case, the wording on the Castrol website spec sheet for their Limited Slip 75w-140 hints that it has a friction modifier in it:

"Advantages - Reduces noise and vibrations in the axle."

Theodore wrote

Can you clarify this? I just completed my differential service and all I saw was the thin green rubber gasket on the drain plug. The differential service had been done before by the dealer. Did they fail to replace some metal washers when they did the service last time?

Green is the gasket. No crush washers on E90M3 diff.

admranger wrote

Green is the gasket. No crush washers on E90M3 diff.

Thanks!


Also wanted to add this to the DIY thread:



Had good luck with this OTC model 2359. Worked great, no leaking, made the job very fast and very easy.

Theodore wrote

Thanks!


Also wanted to add this to the DIY thread:



Had good luck with this OTC model 2359. Worked great, no leaking, made the job very fast and very easy.

I have the same suction gun and it worked great the first time I used it to do transmission oil change but the second time around it started leaking from both ends. I fixed it by putting thread seal tape on both ends.

I did this on ramps at the backend. Drained for half an hour and then filled with 2.4 of the three 500ml bottles before excess started coming out. As I let the excess flow back out, I wondered...why? Seems counterintuitive. I plugged it while it was still flowing back out. Will I have any issues from draining and filling while the car is on ramps, and plugging it when all excess had not escaped yet?

TWiTCHY wrote

I did this on ramps at the backend. Drained for half an hour and then filled with 2.4 of the three 500ml bottles before excess started coming out. As I let the excess flow back out, I wondered...why? Seems counterintuitive. I plugged it while it was still flowing back out. Will I have any issues from draining and filling while the car is on ramps, and plugging it when all excess had not escaped yet?

I would think not. I did the exact same thing you did. My reasoning is that when I first took out the fill plug, the fluid already started to drain for a minute before I took out the drain plug so that means it was already quite full from the previous (first?) time. Anyway, it's been 2 weeks since I changed mine and I haven't had any issues.

Just did this too. Easy stuff. My differential on the OEM fluid started making occasional brrrp noise on right turns, possibly only when cold. Anyway I am on RedLine from ECS now, for LimitedSlip Differentials. If I encounter any problems I'll post.
I also noticed that a good bit of fluid came out of the fill port initially, so before I plugged the fill bolt I shot a pump-load of fluid in and closed it. Let's hope it's not too much but I doubt it. My car's relatively level: ramps and stands.
Had to get a 14mm Allen but Amazon had it (not Sears, not Ace, not HomeDepot).
Edit to add: after several weeks of evaluating, the brrrrp noise is gone from the parking lot turns.

Just bought 3 bottles of differential oil, which came unsealed. Is this normal? Obviously, the content of the bottles can be tampered with, if they aren't sealed. The oil I got is the BMW genuine SAF-XJ + FM booster/SAE 75W-140.