DIY: Differential Fluid Change

Looking at the photos, those looks like torx bolt for the drain and fill.

14mm allen key... no torx!

Dannys M3 wrote

Looking at the photos, those looks like torx bolt for the drain and fill.

driftflo wrote

14mm allen key... no torx!

Yes thats right.. not a torx...when doing fluid change on our E92 m3 from Oil Change, Tranny and Diff uses HEX... no TORX...

Ok thanks, in the photo it looked like a torx.

Fwiw, you can use non FM fluid and if the noises bother you, then add FM later.

ixm3 wrote

Fwiw, you can use non FM fluid and if the noises bother you, then add FM later.

yes exactly and if people that will use the NON FM FLUID... make sure to get one at MERC dealer which is

16 bucks a qtz... compare to 30 bucks a qtz for the FM version...

Is there any significant difference other than the price between the two oils? For example, does the non-FM perform better vs the FM? Better protection? Better performance from the diff?

I'm using the OE BMW fluid while under warranty.

Has anyone used redline or something else in the rear diff? I would imagine that the Redline 75w-140 would work fine.

jjw2331 wrote

Is there any significant difference other than the price between the two oils? For example, does the non-FM perform better vs the FM? Better protection? Better performance from the diff?

I would assume so... I read somewhere that when your diff starts making the noise BMW will use the FM fluid. I say why wait for that noise just use the FM... I have 72k miles on the car and never made a diff noise, and still opted for the FM fluid just for a piece of mind.

bigjae1976 wrote

I'm using the OE BMW fluid while under warranty.

Has anyone used redline or something else in the rear diff? I would imagine that the Redline 75w-140 would work fine.

Yes people have used the REDLINE... they dont have a diff fluid that comes with Friction Modifier but they do have an additive. not sure how much you need to mix it but i think its safer to just get the BMW FM fluid.

the more fm, the less the plates inside the lsd grip (so less noise)... so less locking of course!
it also is aggressive to the oil seal.
so i would only use the fm oil if you really need it and dont want to have noises.

for bmw it is easier and more profitable to sell the fm booster oil and dont have to argue with "customer noises".

if you dont have noise issues or dont mind it, stay with the normal syntrax limited slip for better locking performance and healthy seals!


but when talking about locking performance... if you want a proper performance diff, you will need to swap to a clutch-type lsd anyway... vlsd sucks ;-)

bigjae1976 wrote

I'm using the OE BMW fluid while under warranty.

Has anyone used redline or something else in the rear diff? I would imagine that the Redline 75w-140 would work fine.

I use Redline. It was rec'd by Bimmerworld.

I also use the Redline 75w140, but remember one think is use the redline 75w140 not the 75w140NS !!!

where did you purchase the fluid with FM booster at??

Your dealer should have it or can order it for you. (you need 3 bottles)

Or...

You can order online
http://www.ecstuning.com/BMW-E92-M3-S65_4.0L/Drivetrain/Differential/ES197413/

http://www.turnermotorsport.com/p-2926-genuine-bmw-differential-gear-oil-saf-xjfm-12-liter-500ml-bottle-e46-e9x-m3.aspx

Newbie question but is this the same process for a DCT car? I remember reading somewhere about DCT and 6MT having different diffs...

Red_Baron wrote

Newbie question but is this the same process for a DCT car? I remember reading somewhere about DCT and 6MT having different diffs...

The DCT differential is slightly different in size and has a taller gear from what I understand. However, the process to change the fluid should be the same as well as the differential fluids you use. A quick call to a dealer service foreman should confirm this.

Do the plugs have washers or O-rings? Im assuming new drain bolts come with the o ring and both the drain and fill new replacing once opened?

Also anyone have a copy of the TIS of changing the rear diff oil? That would be awesome!

5soko wrote

Do the plugs have washers or O-rings? Im assuming new drain bolts come with the o ring and both the drain and fill new replacing once opened?

Both plugs have rubber o-rings in them. I've reused them with no leaks but it never hurts to use new ones.

Going to change my diff fluid this weekend. After the initial fill and a short drive is it necessary to open the fill bolt back up and top off the fluid? I've seen conflicting instructions.

Just did this, thanks! Super easy!

Completed my change this weekend and it was very easy but I had a hell of a time getting the drain bolt out. There simply was not enough clearance between that bolt and my exhaust to fit my 14mm socket plus the wrench. The socket I have was just way too long. Ended up going to the hardware store and found a 14mm nut there that was about 2" long. I was able to insert that into the drain plug and put a 6 point box wrench on the other end and twist the plug off. Put the new one on as well, but obviously I couldn't torque to spec.

Apparently this is an issue for a lot of BMW owners and there are specialized stubby 14mm hex sockets for this application. I found one here and placed an order:
http://www.bimmertools.com/Perfect-for-tight-spaces-p/14mmstubby3-8.htm

Just a heads up for you guys. You might want to order one of these beforehand and save yourself some trouble. I'm surprised no one else has mentioned having the same problem.

I ordered a stubby 7mm hex from them for brake changes and it makes life a lot easier. Pricing is a ripoff but couldn't find it elsewhere.

Thanks to the OP for posting this, going to do next weekend.