Oil for rear differential with LSD

[Atle_323i]

Hi,

What kind of oil should I use on my rear differntial with LSD. I can't find any specifications in the manual on what oil should be used.
Says use SAE 90 oil, but GL4? GL5? Castrol brand?

Anyone got suggestion?

[Jeroen]

Preferred juice used to be Castrol SAF-XJ or Castrol Syntrax Limited Sip 75W-140, now superceded by Castrol Transmax LS LL 75W-140.

Alternatives:
MPM Gearbox Oil 75W-140 GL-5 Prem.Synth.Limited Slip
Kroon Gearlube Racing 75W-140 Limited Slip
Royal Purple Max Gear 75W-140 Limited Slip

[Atle_323i]

Preferred juice used to be Castrol SAF-XJ or Castrol Syntrax Limited Sip 75W-140, now superceded by Castrol Transmax LS LL 75W-140.

Alternatives:
MPM Gearbox Oil 75W-140 GL-5 Prem.Synth.Limited Slip
Kroon Gearlube Racing 75W-140 Limited Slip
Royal Purple Max Gear 75W-140 Limited Slip

Great, thanks alot

[uwbuurman]

Well I use the Kroon Classic LS 90, works fine for me.

[Atle_323i]

Well I use the Kroon Classic LS 90, works fine for me.

Ok, that is probably more like a mineral oil type then?
I noticed a BMW webshop in Norway sell, Gulf Gear LS 80W-90, which is a mineral oil type GL-5.
Maybe that oil is more suited for old cars, and the other Jeroen mentioned is for modern style LS diff?

What I´ve read is that GL5 has a higher % of a substance than GL4. GL4 is mentioned somewhere in the E21 manual to be used. But I guess a GL5 probably wasn´t available at the time E21 were made.

[uwbuurman]

Well I use the Kroon Classic LS 90, works fine for me.

Ok, that is probably more like a mineral oil type then?

Yeah,GL05, hypoid, so mineral basic oil, with a few aditives. Especially for te classics. Ls is for the limited slip diffs. I use the ep80 for the gearbox.

[Jeroen]

I was told BMW updated their recommendations for all clutch plate type limited slip diffs to 75W-140 GL-5 as diffs tended to overheat causing excessive wear, but as long as you don't track the car SAE 90 LS will probably be fine.

[Atle_323i]

I was told BMW updated their recommendations for all clutch plate type limited slip diffs to 75W-140 GL-5 as diffs tended to overheat causing excessive wear, but as long as you don't track the car SAE 90 LS will probably be fine.

Ah ok, the car will be used on track now and then, not very much, so maybe just go for the updated version then. As it probably won´t hurt the diff.

[Jeroen]

It will only last longer and be more quiet. This updated recommendation dates back to late later E30 years and these diffs have exactly the same setup as E21 LSD's. If I find this letter from BMW (regular internal tech bulletin, I must have it somewhere) I will post it but that might take a while, too busy schedule for digging through the archives atm.

[Atle_323i]

It will only last longer and be more quiet. This updated recommendation dates back to late later E30 years and these diffs have exactly the same setup as E21 LSD's. If I find this letter from BMW (regular internal tech bulletin, I must have it somewhere) I will post it but that might take a while, too busy schedule for digging through the archives atm.

I'm going to use Castrol 70-140 oil then. And use GL 4 for the gearbox when I replace the oil on the 5 speed that I'm going to use with the 323 engine.

[uwbuurman]

I hereby recall my earlier statements.... I use the Kroon classic EP90 in my regular e30 diff, but have the Castrol 75-140 in my lsd.