Transmission fluid change - the great debate

Voodoomelon

This debate rages constantly on BMW forums, i'm just wondering what the general consensus is here.

Everyone accepts that transmission fluid in autoboxes should be flushed and changed at regular intervals, maybe every 50k miles. No one argues with that.

The problems begin with older autoboxes like in the E38 7 series, that were filled with what BMW called "lifetime fluid", which we all know is a load of crap. BMW have since changed this statement to "100k mile fluid".
However, as it was only recently changed to 100k mile changes and is no longer lifetime fluid, the majority of E38s and other older cars with autoboxes by BMW have never had their fluid changed.

So currently all over the world there are tens of thousands of cars out there with well over 100k miles on the clock and original fluid. The great debate starts when owners ask "is it safe to change my fluid?". And you may ask "why wouldn't it be?".

There are many, many documented cases of these autoboxes with big miles on them having their fluid flushed and changed and then failing within a matter of weeks/months. There are a LOT of suspended particles in this old fluid and apparently keeps the clutch packs running smoothly. Take that fluid away and you have a disaster on your hands.

However there are others with 150k+ miles and they had no problems after their change.
No-one seems to know whether its safe to swap out this fluid on an old car with big miles. If you want that car to last, do you keep on using the old fluid, or do you do a preventative fluid change? If your transmission if giving you trouble at big mileage, do you change it?

What about lower mileage cars, do you do a preventative change at 80k miles (me) and risk killing the box prematurely? The lads on the bimmerforums know SO SO much about these cars, far more collectively than any dealership and no-one can decide on whether its safe or not.

What do you guys think? Thoughts?

Captain Slow IRL

Mine's manual but I changed it at about 80k, at the advice of other owners - was told by BMW it wasn't necessary at the time. There was an improvement changing gear, I'd noticed it was getting sticky which pushed me into changing it in the first place. I find it hard myself to understand how they can call it a lifetime oil, unless the cars have a low life expectancy - once they go out of warranty, I'm sure they don't give a toss about it!

I was talking to a BMW master tech who's been working with bm's for over 25 years, said the auto boxes are very reliable - maybe BMW know what they're at!

When so many people are changing the oil themselves or doing it outside the main dealer network, BMW wouldn't have any knowledge of these oil changes - maybe they just don't hear about it enough to include it as part of a service schedule. (If they did, I'm sure they'd charge you for it if possible!)

Voodoomelon

They are excellent autoboxes the ZFs, very very few failures. I'm leaning towards doing a flush myself now at 80k, I wish I had it done at 69k when I got it but hey.

I reckon I should be alright, but I don't fancy replacing a €5000 gear box, it really puts the sh1ts up me.

unkel

Oooohhh did I spend time researching that one for my E38 V8

Came across very very different owner experiences, but on high mileage V8 E38s the balance was in favour of no-change - imagine that on US biased data!

In the end I decided not to change the tranny oil. The car finally left me for a new home at 141k miles with a gear change still supersmooth.

Owners of 3 and 5 series seemed to have more trouble with their autoboxes with or without oil change, but, owners, please do your own research to make your mind up!

Voodoomelon

See this it is, its all down to mileage, at 141k I certainly wouldn't touch it.
But just look at this Audi A8s ZF tranny pan:

Look at the magnets!


And the fluid! It should be red.

I've been scratching my head for the last few months and I reckon i'll give it a go myself. I reckon 80k is a safe enough interval. I've only just found out that I have the E46s poxy ZF 325Z box so I have to try and track down a unique gasket and filter set.
I hope this goes well...

Anan1

I had a 99 Audi A8 with the 'sealed-for-life' tiptronic box, had the fluid & filter changed at 60k miles. The garage told me the fluid looked awful, I did notice a slight improvement in smoothness but nothing awful. Still worth it even if just for peace of mind, IMO. I can't really see how fresh fluid could negatively effect gearbox life, unless it was airlocked/not refilled properly? From memory it also takes a couple of empty/refill cycles to completely change the fluid, as quite a bit stays in the torque converter even when the transmission is drained.

Voodoomelon

Yup, thats right, nearly half of the fluid fluid remains in the converter. You essentially have to start the car and get the fluid moving through the transmission to get most of it out, while moving between gears.

unkel

Anan1 wrote: »

Still worth it even if just for peace of mind, IMO.

But that's the point - there is no peace of mind. It's not preventative. Many BMW owners had problems after the oil change (and I'm not talking dodgy DIY jobs here). Cause? Who knows, could be anything, any contaminants entering the system during the oil change? I came to the conclusion for myself that as long as the gear change is silky smooth, do not change the oil.

Captain Slow IRL

unkel wrote: »

But that's the point - there is no peace of mind. It's not preventative. Many BMW owners had problems after the oil change (and I'm not talking dodgy DIY jobs here)........

You're only referring to auto boxes?

unkel

Captain Slow IRL wrote: »

You're only referring to auto boxes?

Yes. And only to auto boxes used in BMWs. And only really to auto boxes fitted to the E38

I only researched owner experiences with those boxes...

Volvoboy

Got my auto fluid changed the start of the year, no noticeable diffrence but 14K miles and still working fine. I did go to a main dealer for it tho as indys wouldnt touch it one even said he'd do it but wouldnt be heald responceable if the box broke????

Got it changed at 136K and i really belive it was the original fluid in the box.

Anan1

unkel wrote: »

But that's the point - there is no peace of mind. It's not preventative. Many BMW owners had problems after the oil change (and I'm not talking dodgy DIY jobs here). Cause? Who knows, could be anything, any contaminants entering the system during the oil change? I came to the conclusion for myself that as long as the gear change is silky smooth, do not change the oil.

That's weird, isn't it? Might the change have caused some kind of an airlock in the system, I wonder? I did the same research on Audi forums, and the advice was consistently to change the fluid.

JHMEG

Volvoboy wrote: »

Got my auto fluid changed the start of the year,

Is that in the Toyota? Autobox oil is easier to change than engine oil. I do it every 50k miles, slightly less than 3 litres of ATF-Z1 at about 8 euro a litre. (not talking BMW, or sealed for life)