Transmission oil: LT3 or LT2?

[Mangozac]

OK so I'm planning a fluids refresh on my 2006 M Roadster and decided to go OEM for the transmission fluid. With 10 years and 80k kms the box isn't shifting as smoothly as I'd expect. I didn't order specifically from a part number - I just let the parts guy order it from my VIN (they had to order it in).

I picked up the oil this week and when I got home I realised they have supplied me with MTF-LT3, but everything I have read indicates that the correct fluid is the MTF-LT2. I rang the dealer this morning and he confirmed that according to the BMW database LT3 has now superseded LT2, even specifically for my VIN number, so is insisting that I use this fluid.

Now I have a 2007 TIS version and it specifies the LT2 up to 03/2007, then LT3 from that date onwards. As far as I can tell there only seems to have ever been one transmission BMW part number, which would indicate that there has been no changes to the actual transmissions. This means that it's very feasible that the latest BMW specifications may well be to now use the LT3 for all years of the Z4M.

Can anybody shed further light on this?

[Jaw]

When I was looking at changing the box oil, I was told explicitly LT2 with LT3 being for the 9x beemers as the LT3 is not approved for use in the e46s/85/89..

Strangely it has the same Part number though so many dealers say it superseeds AT-2

[Mangozac]

Yeah that's what I was worried about. For the record, the Z4M gearbox is a completely different unit to the E46 M3 one, so I can certainly sympathise with the comments to NOT use the LT3 for them.

I might get my mate who is a BMW technician to lookup the online TIS (or whatever it's called these days) and see what it says...

[Mangozac]

OK so an update on this:
The current technical system specifies LT2 up until 2007 and LT3 from there onwards.

I called Brisbane BMW and the parts interpreter there told me that as far as he can tell the LT3 does NOT supersede the LT2. My transmission has the LT2 sticker on it so that's what I need to use.

So now I need to take these bottles of LT3 back to swap them for the right stuff....

[GuidoK]

You should only use the mtf lt3 oil if you have a blue sticker on your gearbox.
yellow&green=mtf lt2
orange = ATF

[Mangozac]

We have another twist in the transmission oil saga! The LT2 fluid isn't stocked these days so it has to come out of Germany. That's a long wait for us here in Australia, so I did some more digging on my original hunch.

All 6 speed models of Z4 use the same manual transmission unit, just with minor differences (apparently generally external things like flanges and linkages) denoted by the 4-letter suffix. 03/2007 is the formal changeover date for specification of the LT3 transmission fluid, yet the BMW part number for the transmission is identical before and after this date.
2006 Z4M uses transmission GS6-37BZ - TJEE, part no 23007837983, fluid=LT2 (RealOEM)
2008 Z4M uses transmission GS6-37BZ - TJEE, part no 23007837983, fluid = LT3 (RealOEM)
2006 3.0si uses transmission GS6-37BZ - TJES, part no 23007565178, fluid = LT2 (RealOEM)
2008 3.0si uses transmission GS6-37BZ - TJES, part no 23007565178, fluid = LT3 (RealOEM)

I have a knowledgeable friend who is an E46 M3 owning BMW technician so I had a chat with him about it last night. Our conclusion is that BMW did extensive testing of compatibility between the LT3 fluid and GS6-37BZ transmission but formal specification of this did not occur until 03/2007. As best I can tell both fluids are the exact same weight. There is no reason the LT3 shouldn't be fine in the 2006 Z4s.

Contrast this with the E46 M3s. There is much debate on the suitability of the LT3 in that application, with some dealers saying that you can use LT3 and other dealers saying not to. The transmission used in the E46 M3 wasn't used past 2006 and therefore BMW would not have done extensive compatibility testing with the LT3 fluid. It would probably be fine too, but to play it safe in this case they are best to stick with the LT2.

Another point of interest on the above RealOEM links is that no matter which fluid is specified it seems that only the LT2 sticker is ever specified!

So after all of that I'm going to run with the LT3 that I have.

[GuidoK]

As best I can tell both fluids are the exact same weight.

MTF-LT2:



MTF-LT3:



Not the same if you read the label.
Almost the same although labels can also be incomplete.

I dont know how it is in australia, but here you can get mtf-lt2 spec oil from a vast amount of suppliers. Like castrol etc (and usually a lot cheaper than bmw oil bought at the stealer...).
A transmission oil like CASTROL SYNTRANS B 75W is mtf-lt2 specced but not mtf-lt3. Mind you, to put these specs on a bottle you have to pay bmw for it (its a commercial oil spec). So either they didnt pay for it, or it isnt within spec for MTF-LT3.
On the other hand if you look at Mannol MTF-4, it is specced for both mtf-lt2 and mtf-lt3.

BTW there are definately z4 gearboxes that have the blue sticker on there (but this is not the same box as the z4m has)
See this auction:
http://www.ebay.de/itm/BMW-Z4-2-5si-E85 ... 1915731657

Personally I'd always stick with the prescribed standards (so what it says on the sticker) as synchromeshes in manual transmissions can be finicky (modern synchromeshes have a clutch type material inside what grabs the gear to synchro the speed; the amount of grab needs to be right)

[Mangozac]

Thanks for the comments, Guido. I enjoy this kind of discussion (even if I may be coming across as a little pig-headed in my intention to stick with the LT3)

Not the same if you read the label.
Almost the same although labels can also be incomplete.

Same viscosity when cold, but why is no hot viscosity specified for the LT3? Is that common?

I dont know how it is in australia, but here you can get mtf-lt2 spec oil from a vast amount of suppliers. Like castrol etc (and usually a lot cheaper than bmw oil bought at the stealer...).
A transmission oil like CASTROL SYNTRANS B 75W is mtf-lt2 specced but not mtf-lt3. Mind you, to put these specs on a bottle you have to pay bmw for it (its a commercial oil spec). So either they didnt pay for it, or it isnt within spec for MTF-LT3.
On the other hand if you look at Mannol MTF-4, it is specced for both mtf-lt2 and mtf-lt3.

Yeah, products like these that have BMW specs on them are rare here. Neither the Mannol or the Castrol are available (and Castrol list nothing that I would feel any more confident with than the OEM LT3).

BTW there are definately z4 gearboxes that have the blue sticker on there (but this is not the same box as the z4m has)
See this auction:
http://www.ebay.de/itm/BMW-Z4-2-5si-E85 ... 1915731657

Interesting, but according to RealOEM the 2.5i/si box had the LT3 sticker specced from start of production (of N52 engines).

Personally I'd always stick with the prescribed standards (so what it says on the sticker) as synchromeshes in manual transmissions can be finicky (modern synchromeshes have a clutch type material inside what grabs the gear to synchro the speed; the amount of grab needs to be right)

That's a good rule of thumb to go by, but it seems that this may become harder to do as the LT2 gets older (certainly here in Australia). Bottom line is that worst comes to worst the synchromeshes don't like the LT3 fluid and I have to change it again soon. The LT3 fluid certainly isn't going to cause damage in the Z4M's transmission.

[GuidoK]

Thanks for the comments, Guido. I enjoy this kind of discussion (even if I may be coming across as a little pig-headed in my intention to stick with the LT3)

Not the same if you read the label.
Almost the same although labels can also be incomplete.

Same viscosity when cold, but why is no hot viscosity specified for the LT3? Is that common?

Only on a multigrade oil a hot viscosity is specified. Single grade oils per definition not.
But 75w80 is only ample multigrade of course.

[Mangozac]

Only on a multigrade oil a hot viscosity is specified. Single grade oils per definition not.
But 75w80 is only ample multigrade of course.

I'm embarrassed how obvious that is!