Diff oil...

[miniblob]

I know this has been on here before - probably hundreds of times, but I'm struggling to find it with the search facility!!!

So.... what oil/fluid is best/recommended for replacing the fluid in a used 3.91 LSD??? And how much will it need???

Come to think of it - would it be the same for the gearbox - or what fluid and how much would I need for that too???

Thanks in advance!!!

[Grrrmachine]

Search is rubbish, but if you put three letters into the Wiki search, you get all your answers:

http://www.e30zone.net/e30zonewiki/index.php/Oil

[miniblob]

Ha - top man!!! Cheers!!!

[broadie]

ATF dextron2 for a getrag manual box. If you want it change gear from cold.

[Brianmoooore]

ATF dextron2 for a getrag manual box. If you want it change gear from cold.

Only if there is a problem with cold changes. Most are fine.

[harry_p]

Hmm, I'm not sure the wiki is correct.

A plate type LSD diff ( like all e30 ones ) MUST use a gear oil designed for limited slip differentials. Simply saying 70w140 is not good enough. A normal gear oil will destroy the plates and make it work like an open diff.

Castrol racing b373 of saf-xj ( which I believe has now been superseded ) are the recommended oils for an LSD.

Edit, castrol b373 is an extreme pressure mineral oil designed for limited slip diffs.

Saf-xj is now called syntrax limited slip and is fully synthetic. I believe you can still buy saf-xj from bmw, or as old stock, but most places will now sell syntrax limited slip 70w140 instead.

[Brianmoooore]

Wiki is indeed incorrect, and what harry_p says is the correct version.

[craigieeb]

So would the likes of this be any good...

http://www.opieoils.co.uk/p-888-motul-9 ... ssure.aspx

[Brianmoooore]

The description of that oil specifically says to use a different oil.

[bmw-mad]

opie oils sell this

http://www.opieoils.co.uk/p-736-castrol ... w-140.aspx


BMW don't seem to sell LSD oil In small amounts any more they want to sell a big drum

[zd3bx]

I used Castrol 75w-140 in my LSD, no probs.

Had to buy 2 ltr, as the diff takes around 1.7.

[Grrrmachine]

Wiki updated. Thanks for the info harry

[Brianmoooore]

Unless it's been rebuilt, it won't really matter if you use a LSD specific oil or not in an E30 slipper, since it will almost certainly have very little LS action left.
I have two E30s with unrebuilt LSDs. The one I've 'tested' won't ever move the car off the line if one rear wheel is on grass, and the other is so ineffective I didn't even know the car had one until a random check on a " find your original build spec." web site told me it had, which I subsequently confirmed.

[hennabm]

After replacing my diff cover last year, I checked the spec for my LSD with the dealer and 75/140 fully synthetic was the answer.
The best the off the shelf fluid in the likes of GSF etc, I could find was 75/90 so I went back to the dealer.

They very nicely gave me 2 litres to ensure I had enough to refill.

[harry_p]

opie oils sell this

http://www.opieoils.co.uk/p-736-castrol ... w-140.aspx


BMW don't seem to sell LSD oil In small amounts any more they want to sell a big drum

I have heard before that bmw don't sell oil separately, yet if you had a service there they'll happily invoice you for the amount used and not a whole drum.

Some places sell it bottled, other places you need to provide your own container, others don't want to know unless you're paying them £75 per hour plus oil for them to do it for you..

Personally, in an old tech diff like an e30s I would ( and have ) happily use a high performance mineral oil like b373, and just replace it more often.

More frequent changes are more important than the ultimate technology on what is designed to be a wearing part, unless you're putting it under considerably more stress than it was originally designed for, in which case a fully synthetic will give optimum protection.

Last time I looked, b373 was between 1/2 and 1/3rd the price of saf-xj.

[Brianmoooore]

As I understand it, the problem with the wrong oil is nothing to do with wear rates, but to do with the friction properties of the oil on the plates of the LS pack. 'Ordinary' oil causes the plates to judder as they slip, while the correct oil, with a 'friction modifier' additive, allows the plates to slide smoothly. This ties in nicely with the banging noise, when turning sharply, that has been reported on here on occasions, after diffs. have been refilled with the wrong stuff by uninitiated mechanics after a service.

[BenHar]

The sticky from Opie at the top of this section has a link to the specs.

http://www.e30zone.net/modules.php?name ... c&t=122178

links to:

http://www.opieoils.co.uk/c-688-bmw.aspx

further drilling goes to:

http://www.opieoils.co.uk/p-736-castrol ... w-140.aspx

That's what you need for an LSD.

Ben