Help me identify my diff

[Zephyr]

Reads (possibly) 12128811 or 1212881F
No other data on it.
looks like the ratio is 3.46 (turned the wheels and calculated).
acts as an LSD when I rev and let go
acts as an open diff when I rotate the wheels by hand…
Quite puzzled…

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ibb.co

 

[motco]

If by 'it acts like an open diff...' you mean that turning one wheel turns the other in the opposite direction then it may well be an open diff. If, however, you mean one wheel turn the other in the same direction then (I seem to recall) it's a 'proper' LSD. The most likely though, is a Torsen diff on which there appears to be no effect of one wheel by the other. Many Z3s have that sort of diff. I would describe it as a 'soft' LSD.

 

[Duncodin]

There was a post a couple of days ago. @Lee I think it was. He explained that one of the diff types is an LSD but behaves like a non LSD when the wheels are off the ground - or something like that.

 

[Zephyr]

It acts as an open when the car is lifted, but leaves two fine marks on the ground when I rev and let go.

 

[Zephyr]

There was a post a couple of days ago. @Lee I think it was. He explained that one of the diff types is an LSD but behaves like a non LSD when the wheels are off the ground - or something like that.

Yes. He explained in detail. But it still bothers me that I can not identify the diff by serial number or other marks.
i will have to open it and check.
i need to change the fluids so want to be sure, because I think that the shop put the wrong oil in it.
i checked my receipts, called them and they said they thought it was an open diff…
So thats why I am overreacting.
sorry for being a pain

 

[DrWong]

Re: oil, I’ve read normal diff oil is fine for Torsens and that proper LSD oil is only needed for plate clutch LSDs, which are only found on M Roadsters as far as Z’s are concerned.

So you may be ok, but this is just what I’ve read and needs confirming/refuting by someone more knowledgeable than me.

 

[the Nefyn cat]

Yep, normal diff oil for Torsens, special LSD oil for plate clutch types.

 

[Zephyr]

Thanks guys. Finally I can sleep tonight.

 

[DrWong]

Yep, normal oil for Torsens, special LSD oil for plate clutch types.

Do you know if the opposite is acceptable, i.e. can LSD oil go into a Torsen?

I've got 2 litres of Castrol Syntrax 75w-140 on the shelf that I bought before I found out normal oil is fine. Just wondering if it would do any harm to put into my diff (which is a Torsen)

 

[the Nefyn cat]

There wouldn't be any point putting LSD oil in a Torsen, it's a special type for use with a plate clutch, which would slip too much with a conventional diff oil. The Torsen-type diffs don't have any friction plates, as it's a purely mechanical thing. The youtube video will explain it better than I can, the diffs are way cleverer than me.

View: https://www.youtube.com/watch?v=JEiSTzK-A2A

 

[DrWong]

I've already bought the special diff oil in error but not used it yet. If it's fine for a Torsen though, I'll happily put it in and save myself the cost of buying the conventional oil, hence the query. I bought the oil a couple years ago so no prospect of exchange/refund.

Seen that video before - it's ace! Agreed the Torsen is a v. clever thing.

 

[motco]

The question I have never received a definitive answer to, even from the Torsen technicians, is can the brakes be tested on the rollers at MoT time or should it be done with the Tapley tester on the floor of the footwell? My MoT place uses the Tapley for the sake of safety.

 

[Brocky61]

Found this on a PDF copy of the Z3 workshop manual I bought off ebay, regarding Differential oil. Says that Z3 LSDs require SAF-XJ

 

[Brocky61]

Found this on a PDF copy of the Z3 workshop manual I bought off ebay, regarding Differential oil. Says that Z3 LSDs require SAF-XJ

View attachment 260193

Based on the above, I just put this (SAF-XJ+FM) in my 3.0 diff. It's very light in colour compared to the very dark treacle coloured stuff I drained out.