Diff oil for the upgraded Clutch-type differentials?

[RevUpp]

Hi guys, I´m having a grinding noise on closed turns that I suppose could come from the rear diff.

I have been told by the previous owner that my E46 M3 has the rear diff modified to a Cluth type , and as I was going to buy the usual Castrol SAF-XJ + FM Booster used with M3 with regular diffs, now I´m not sure if this is the proper oil for this modified differential.

Any of you with a cluth type diff could help me with this? What, if not this, is the proper diff oil?

Thanks in advance

[zivagolee]

On my diffsonline 3 clutch diff, they recommend redline 75w-110 so that is what I use.

[STAATS]

Well normally if you have a clutch type it is a modified E36 M3 core or from another BMW 210mm diff that was clutch based instead of viscous based like the E46 M3 diff so technically if you want to be all legit you should use what is specc'd for that diff. I believe OE fill for E36 M3 diff is Castrol SAF-XJ 75W-140

I have a Drexler Motorsport diff (clutch type obviously) and the advice from them regarding Diff Oil is:

Regarding the oil you you can use either of these two:
- Ravenol SLS SAE 75W-140
- Castrol Syntrax Limited Slip 75W-140…

Based on this I went with Castrol Syntrax Limited Slip 75W-140

So basically you can do a standard E46 M3 Diff fill just without the FM Booster... The FM Booster was only ever to reduce the noise made by the E46 M3 diff anyway... I wouldn't use it in a purely clutch pack diff unless the manufacturer specifically designed the clutches for FM... given its most likely a E36 M3 diff core or derivative this would not have been designed for FM so I wouldn't bother. I can confirm I have no noticeable noise from my Drexler Motorsport diff and I am not using FM.

All of the above said... the key ingredient is the diff oil grade of 75W-140... everything else such as brand, FM or no FM isn't really a huge deal unless you're at that 10/10ths level. So while my advice is Castrol Syntrax Limited Slip 75W-140 if you can say get Motul or Liqui Moly or Ravenol of the same spoec cheaper and easier then I would go with that. Regular servicing is more important.

Blackstone has previously written a report after years of analysis and reporting confirming that the most important part is the grade... same grade different brands have no real discernable difference in wear according to their data... although this is always hard to swallow as there is heaps of anecdotal evidence of more people spinning bearings using Redline vs Castrol or the engine running hotter with LiquiMoly or whatever.

[RevUpp]

Well normally if you have a clutch type it is a modified E36 M3 core or from another BMW 210mm diff that was clutch based instead of viscous based like the E46 M3 diff so technically if you want to be all legit you should use what is specc'd for that diff. I believe OE fill for E36 M3 diff is Castrol SAF-XJ 75W-140

I have a Drexler Motorsport diff (clutch type obviously) and the advice from them regarding Diff Oil is:



Based on this I went with Castrol Syntrax Limited Slip 75W-140

So basically you can do a standard E46 M3 Diff fill just without the FM Booster... The FM Booster was only ever to reduce the noise made by the E46 M3 diff anyway... I wouldn't use it in a purely clutch pack diff unless the manufacturer specifically designed the clutches for FM... given its most likely a E36 M3 diff core or derivative this would not have been designed for FM so I wouldn't bother. I can confirm I have no noticeable noise from my Drexler Motorsport diff and I am not using FM.

All of the above said... the key ingredient is the diff oil grade of 75W-140... everything else such as brand, FM or no FM isn't really a huge deal unless you're at that 10/10ths level. So while my advice is Castrol Syntrax Limited Slip 75W-140 if you can say get Motul or Liqui Moly or Ravenol of the same spoec cheaper and easier then I would go with that. Regular servicing is more important.

Blackstone has previously written a report after years of analysis and reporting confirming that the most important part is the grade... same grade different brands have no real discernable difference in wear according to their data... although this is always hard to swallow as there is heaps of anecdotal evidence of more people spinning bearings using Redline vs Castrol or the engine running hotter with LiquiMoly or whatever.

Thanks STAATS

Yup, I have the Castrol Syntrax Limited Slip 75W-140 alone (without the FM) so I guess I can use it with the clutch type diff...

Years ago I had another M3 with the original diff and the mix of this same oil + the FM additive was the cure for the grinding noise, I was always guessing that the clutch type diffs didn´t suffer the same grinding sympthoms, but I´m new with the clutch type diffs and maybe it´s possible..

[CrookedCommie]

Another option is the Motul Gear Competition 75W-140. What I'm using in the racingdiffs lsd.

[bigjae46]

Thanks STAATS

Yup, I have the Castrol Syntrax Limited Slip 75W-140 alone (without the FM) so I guess I can use it with the clutch type diff...

Years ago I had another M3 with the original diff and the mix of this same oil + the FM additive was the cure for the grinding noise, I was always guessing that the clutch type diffs didn´t suffer the same grinding sympthoms, but I´m new with the clutch type diffs and maybe it´s possible..

FM is friction modifier. The OE XJ+FM fluid has more FM in it to address low speed groaning noises in the LSD unit. If you can, check with the diff builder FIRST. I'd recommend a synthetic 75w-140. If you get some groaning at low speeds and turning sharply, go with the OE XJ+FM fluid.

Keep in mind, FM will affect how the LSD unit locks. In a ZF clutch diff, it makes a different. You get less lock with more FM.

[RevUpp]

FM is friction modifier. The OE XJ+FM fluid has more FM in it to address low speed groaning noises in the LSD unit. If you can, check with the diff builder FIRST. I'd recommend a synthetic 75w-140. If you get some groaning at low speeds and turning sharply, go with the OE XJ+FM fluid.

Keep in mind, FM will affect how the LSD unit locks. In a ZF clutch diff, it makes a different. You get less lock with more FM.

Thanks Bigjae46. Finally I´ve been in touch with the diff builder and he told me that the mix of OE 75w140 + FM fluid doesn´t applies to the clutch style dif, he recommended the Red line 75w140 or Mobil 1 75w 140 which performs better than the Castrol 75w 140

[RevUpp]

Another option is the Motul Gear Competition 75W-140. What I'm using in the racingdiffs lsd.

Thanks CrookedCommie