Differential fluid question

[Doc Oc]

Hi all, I just drained and refilled my diff but I'm a little concerned as everything I've read says it takes 2.5 QTS to fill, however at 1.5 QTS the fluid started coming back out of the fill hole. Normal? 2008 m3 dct.

Thanks

[jimk]

Originally Posted by Doc Oc

Hi all, I just drained and refilled my diff but I'm a little concerned as everything I've read says it takes 2.5 QTS to fill, however at 1.5 QTS the fluid started coming back out of the fill hole. Normal? 2008 m3 dct.

Thanks

It is 2.5 pints or 1.25 quarts.

http://www.amsoil.com/mygarage/Vehic...=2008+BMW+M3+N

[Hujan]

Originally Posted by jimk

It is 2.5 pints or 1.25 quarts.

http://www.amsoil.com/mygarage/Vehic...=2008+BMW+M3+N

What he said. It's a lot less than you think.

[Doc Oc]

Duh....thanks guys

[Doc Oc]

So after switching over to redline 75w140 (not ns) I now have a grind/clunk come from the lsd when I make a tight right turn. Never heard it before switching the fluids. Guess I need to go back to stock oil?

Thanks

[M3Bimmer77]

Try draining some fluid and replace it with a FM, friction modifier. From the same brand. You guys need to use the SAF-XJ with FM in our cars.

[TZANIDO777]

Originally Posted by Doc Oc

So after switching over to redline 75w140 (not ns) I now have a grind/clunk come from the lsd when I make a tight right turn. Never heard it before switching the fluids. Guess I need to go back to stock oil?

Thanks

I also replaced the stock fluid with Redline 75W140 and are experiencing grinding/clunking only during tight right hand turns.

[KFN]

Originally Posted by TZANIDO777

I also replaced the stock fluid with Redline 75W140 and are experiencing grinding/clunking only during tight right hand turns.

Same here, Same oil, same noise. There are a few threads on the subject. From what I understand the noise is just a nuisance and not an indication of anything wrong - just tight clutches (at least that's what I'm telling myself). I personally skipped the friction modifier.

[s85e90]

No noises at all running Royal Purple.

[TZANIDO777]

Originally Posted by KFN

Same here, Same oil, same noise. There are a few threads on the subject. From what I understand the noise is just a nuisance and not an indication of anything wrong - just tight clutches (at least that's what I'm telling myself). I personally skipped the friction modifier.

I have been the reading the same...something about some clutch packs not being fully lubricated by the oil and when they rub together they cause that grinding/clunking noise were are experiencing.

I purchased the diff oil with the friction modifier from BMW but I have yet to install it to see if it remedies the problem.

[Doc Oc]

So is this as easy as adding an ounce or two of fm or is this fluid just not what we need to be running? I've got the fm on order but don't mind switching back over to stock or going rp if that's a better bet.

[5soko]

Make sure when you fill, once the fluid starts coming out the fill hole to let it to continue to come out until it stops, or you will be over filling and it might leak out from the seals... The fluid is suppose to be level with the fill hole, not seeping out like most think..
+1 with fluid with FM in it

[Doc Oc]

Originally Posted by 5soko

Make sure when you fill, once the fluid starts coming out the fill hole to let it to continue to come out until it stops, or you will be over filling and it might leak out from the seals... The fluid is suppose to be level with the fill hole, not seeping out like most think..
+1 with fluid with FM in it

Good info, didn't know that!

[admranger]

Originally Posted by 5soko

Make sure when you fill, once the fluid starts coming out the fill hole to let it to continue to come out until it stops, or you will be over filling and it might leak out from the seals... The fluid is suppose to be level with the fill hole, not seeping out like most think..
+1 with fluid with FM in it

It's not going to leak out the seals unless they are bad. The diff has a vent so it doesn't pressurize as thing heat up (and diffs get hot on the track!).

Worse case is you'll spit a bit of fluid out the vent, but even on when I raced that was very, very rare.

So, once the fluid starts running back out, pull your hose out and put the plug in and torque to spec. Don't sweat having an ounce or two too much fluid in there.

[Doc Oc]

OK, thanks

[5soko]

Originally Posted by admranger

It's not going to leak out the seals unless they are bad. The diff has a vent so it doesn't pressurize as thing heat up (and diffs get hot on the track!).

Worse case is you'll spit a bit of fluid out the vent, but even on when I raced that was very, very rare.

So, once the fluid starts running back out, pull your hose out and put the plug in and torque to spec. Don't sweat having an ounce or two too much fluid in there.

Unfortunately this was the common knowledge if over filled, it would just spit it out threw the vent. But in the case of me and my friend, after we both changed our fluid to OEM +FM fluid, we just filled until it spilled out and locked her up... While after, drip on garage floor and wet bottom diff... remove plug, let excess fluid spill out until evel with fill hole, button her back up... No wet diff or leak 5K miles for both of us.. vent hole was dead dry on both our diffs, wonder if they get clogged easy or something or if the vent is too high on the diff for the fluid to escape. So in my experience i have always told everyone to wait until it stops coming out just to be safe, and its technically following the BMW TIS instructions correctly anyways.

[admranger]

Originally Posted by 5soko

Unfortunately this was the common knowledge if over filled, it would just spit it out threw the vent. But in the case of me and my friend, after we both changed our fluid to OEM +FM fluid, we just filled until it spilled out and locked her up... While after, drip on garage floor and wet bottom diff... remove plug, let excess fluid spill out until evel with fill hole, button her back up... No wet diff or leak 5K miles for both of us.. vent hole was dead dry on both our diffs, wonder if they get clogged easy or something or if the vent is too high on the diff for the fluid to escape. So in my experience i have always told everyone to wait until it stops coming out just to be safe, and its technically following the BMW TIS instructions correctly anyways.

Where'd the leak originate from and why did it miraculously disappear after draining some fluid? Fluid is splashed all over the diff during driving, so I'm struggling with the cause of the leak. I don't doubt you experienced it, but I have a hard time believing the minimal static fluid pressure alone would have led to a leak that wouldn't persist upon driving (maybe to a lesser extent, but it would have leaked).

Interesting info nevertheless.