New differential oil

[vuk8691]

Hi,
I own M3 E92 2008. Recently, there were broken bearings on the rear differential, and I ordered a new differential. I plan to first oil change at 2000 km. Is it necessary to use expensive BMW oil with FM booster or it's not necessary?

[s85e90]

No not necessary. I run Royal Purple 75/140 and it's been great and quiet for over 2 years.

[vuk8691]

Originally Posted by s85e90

No not necessary. I run Royal Purple 75/140 and it's been great and quiet for over 2 years.

Thank you.

I assume that the oil with FM booster required only in older differentials that make sounds when cornering?!That was the case with my differential.

[thekurgan]

I wouldn't use the FM crap unless you have excessive chatter. Groaning is normal and welcome as a diff noise.

[nekky]

I used the expensive FM crap but only because I got a free diff flush out of the deal. Diff still groans but hard to tell how much if less it has subsided.

[Sandye90m3]

Originally Posted by thekurgan

I wouldn't use the FM crap unless you have excessive chatter. Groaning is normal and welcome as a diff noise.

Is there a reason why you think that? Not trying to argue here, but sincerely want to know. From my understanding, the FM booster is supposed make the diff run smoother, and it most probably does because that is the intent of that product.

Everything is done for a reason, BMW obviously picked the FM booster for a reason...

[s85e90]

Originally Posted by Sandye90m3

Is there a reason why you think that? Not trying to argue here, but sincerely want to know. From my understanding, the FM booster is supposed make the diff run smoother, and it most probably does because that is the intent of that product.

Everything is done for a reason, BMW obviously picked the FM booster for a reason...

It's an additive to quiet the diff working so yes it's effectively reducing the diffs effectiveness. It shouldn't be used automatically unless warranted. Most A/M fluids come with it preinstalled.

[jjw2331]

Originally Posted by Sandye90m3

Is there a reason why you think that? Not trying to argue here, but sincerely want to know. From my understanding, the FM booster is supposed make the diff run smoother, and it most probably does because that is the intent of that product.

Everything is done for a reason, BMW obviously picked the FM booster for a reason...

They started with Castrol SAF-XJ which is essentially the BMW labeled FM booster fluid without the FM booster. If you complained about diff noise, only then would BMW put in FM booster fluid into your diff. About 4 years ago they updated the service bulletin to just put the FM booster fluid in without complaint.

So this FM boosted fluid was not intended. Most diff builders will tell you it reduces locking which is what you do not want.

[thekurgan]

What those guys stated. Folks complained about groaning coming from such an expensive car, even though the groaning was a good sign of a working limited slip diff, and BMW came out with a "silencer', that allows more slip. I've never used it on my past 4 M diffs.

[vuk8691]

Is the only BMW M3 have problems with differential or is the case with all BMW vehicles?

[thekurgan]

Originally Posted by vuk8691

Is the only BMW M3 have problems with differential or is the case with all BMW vehicles?

What problems?

[vuk8691]

Originally Posted by thekurgan

What problems?

My differential bearings broken at 85000 km and I have to buy new differential. I had many other cars with even 200000 km and never had thing like that.

[thekurgan]

Originally Posted by vuk8691

My differential bearings broken at 85000 km and I have to buy new differential. I had many other cars with even 200000 km and never had thing like that.

The diff is a wear item, were your other diffs open or limited slip? I've never had one last to 100k as a limited slip without clutches needing replacement.

[vuk8691]

I do not understand very much about the mechanics. Is the only M3 has lsd? Why?

[Z K]

I am running the regular non-FM fluid. I had some diff chatter before and the dealer but in the FM fluid. The chatter went away. At my next diff service interval, I switched back to the non-FM fluid and it's been fine.

The chatter is normal for clutch type LSDs. Adding the FM fluid reduces the performance of the diff when it tries to lock. It's not necessary if your diff is not making noises. Even if it is, go do some performance driving and the noise will go away once the diff warms up.

Only the M models cars like the M3 has an LSD. It adds performance to the car. The regular models don't have it. Probably because normal people wouldn't use the performance anyway. Saves BMW money.

[vuk8691]

Originally Posted by Z K

I am running the regular non-FM fluid. I had some diff chatter before and the dealer but in the FM fluid. The chatter went away. At my next diff service interval, I switched back to the non-FM fluid and it's been fine.

The chatter is normal for clutch type LSDs. Adding the FM fluid reduces the performance of the diff when it tries to lock. It's not necessary if your diff is not making noises. Even if it is, go do some performance driving and the noise will go away once the diff warms up.

Only the M models cars like the M3 has an LSD. It adds performance to the car. The regular models don't have it. Probably because normal people wouldn't use the performance anyway. Saves BMW money.

Thanks for the explanation.

[ItsCoo2PYoPants]

whats the capacity for the diff?