ZF8 Fluid Changed

[Grumpyjohn1957]

Followed the ZF recommendation of 60k fluid refresh. Genuine ZF pan, oil and electrical connector sleeve.
A ½ ltr sample of the old fluid retained for analysis.

The drained fluid is a cloudy dark grey – suggestive of fines in suspension - in a test tube when illuminated from behind the fluid has more than a hint of green to it. The odour is essentially sweet oily with an extremely faint suggestion of burning. Pan spotless, no evidence of gelling, precipitation, emulsification, no metallic deposits in the filter.
The used fluid is highly mobile and free flowing, so much so it would probably serve as a good penetrating oil.

Driving wise there is a difference. At tick over the box is definitely quieter, overall the car seems smoother.
For the first 50/70 miles though, particularly in town traffic, the change pattern was noticeably different. Abruptness and hesitation were apparent in all modes (sport, comfort and eco) especially from rest 1-2-3, but strangely this was much reduced when manually shifting.

Day-to-day use in conjunction with repeated coasting from 8 to 1 without brakes followed by gentle acceleration to 8th numerous times appears to have retrained the adaptations somewhat.

After 350 miles or so the shifts started to become indisputably smoother and definite. Furthermore, the box became more responsive to kicking down and long slow pedal depressions. The car changes gear more frequently and is doing so at lower rpms than pre service. When new, steady acceleration would invoke a change at 1100/1200rpm as opposed to the 1400/1500rpm seen latterly. Under sudden throttle, but not full kick down, its now immediately skipping down two, sometimes 3 cogs for instant power.

From the visual condition of the fluid, I’m fairly confident no excess mechanical wear has occurred to cogs, bearings, or clutches. Full fluid analysis would confirm or refute this. It would be interesting to have the box checked electronically to see how closely the solenoid’s function and the pressures hold compared to original factory specifications.

Overall then? It’s better, not night and day, just better and back to its original self.

Conclusions with benefit of hindsight:

In hard usage scenarios ZF recommend changing the fluid at 40K miles. Towing, hot climates and sporty driving are stated examples. Given the heat and enormous forces of shear and compression fluid is exposed to in machines as powerful as unleashed B3’s B5’s or M cars, it stands to reason it will degrade far quicker than when used in a regular three litre.

Oil analysis would show the extent of any degradation but despite my aching curiosity in this case, I’m a little reluctant to pay for it.

My “take away” is it would have been better to have changed the fluid at 40K as demonstrated by the extent to which the gearbox had to relearn its adaptations before returning to silky normal. Swapping fluid should have made little or no difference to the user experience.

If you have a particularly powerful car which you frequently enjoy, then my advice would be to change the fluid at 40K. If you always drive “normally” change it at 60K or 80k. With a less powerful model I’d suggest that waiting for the BMW lifetime of 100K is fine.

A fellow forum member made a comment to me a while back along the lines of “How Alpina would choose to specify maintaining their cars as opposed to how BMW one size fits all servicing Is applied to their cars are total opposites” he’s right.

Note: In this instance the gearbox adaptations were not reset. I was advised doing so could cause issues without explanation of what they might be.

[MattOz]

Hi John,

Where did you get this done? Was it local(ish)? I'm looking to get it done to my car and if i can minimise travel time to get it done, that would be great.

Cheers
Matt

[Grumpyjohn1957]

Hi Matt
Not that local to either of us!
I use Autotechnik of Lutterworth, BMW/Mini specialist indies. They do my intermediate/other work and have looked after all my previous BMs. They've seen a few Alpinas so I'm comfortable. Courtesy cars available, had to leave it overnight so it was cool enough to do correctly.

[MattOz]

Thanks John.

It’s either there, or another trek to BMR in Crawley.

[Frosty]

What sort of money are we looking at to get this done, if you don't mind me asking? I am not sure mine has ever been done!

[Grumpyjohn1957]

Fluid 9ltr, Pan, Sleeve, £420

[Frosty]

Cheers. Think I will have to see about getting booked in at somewhere like BMR as I also noticed a weeping diff seal too.

[Grumpyjohn1957]

Curiosity finally got the better of me, I had the used gearbox oil analysed.
In isolation this result is somewhat meaningless, there’s no baseline (unused oil) and until I pull another sample from the box no comparable. Having looked at the result and gulped slightly, a bottle of ZF8 is on the way. Soon as the weather warms up I’ll be wriggling underneath to pull a sample of what’s in there now. (Approaching 10k miles of use).
The latest sample will be interesting. Dropping the pan is not a complete drain & flush. The torque convertor would remain at least part filled as would the transmission cooler and mechatronic. Despite some 7 or 8 litre going back in I’m presuming there’d be at least 20% of old stuff still in the works.
On emptying the box my first observation was how cloudy the drained oil looked, suggesting stuff in suspension. I haven’t any ash filter papers to run it through so I can’t gauge the particle sizes. It doesn’t smell burnt or “clutchy” It’s mobile and still green when a strong light is shone through it. 3 months of the container sitting on a strong magnet didn’t result in any iron filings or the like.
Staring at it and sniffing it led me to speculate it wasn’t cooked, sheared, contaminated with water and the fines must be metallic. The analysis bears this out but the wear metal content scares the Bejesus out of me. The only thing I could find online relating to what one might see in a gearbox oil analysis came from Blackstone and is listed below, it makes no mention of actual levels and I’m presuming my report is in ppm (forgot to ask)
Wear Metal Sources
Aluminium: Housing, bearings, oil pump, gear and vane pumps
Cadmium: No info. Possible contaminant in the base oil?
Chromium: Ball and roller bearings, alloy of steel parts like gears
Copper: Bronze bushings, oil cooler oxides, clutch plates, brass fittings
FW Index: A way of measuring larger Ferrous particles
Iron: Gears, bearings, shafts, some cases, clutch plates
Lead: Residual gear marking compound, alloy of bronze
Nickel: Clutch bands, gear/shaft steel alloy Tin: Some bearing cages, alloy of bronze
Silver: Some soft friction bearings, Allison needle bearings
Tin: Soft bearings
Vanadium: Found in the coating of parts like valves, rods, rings, and bearings
Manganese: Alloy of steel
Titanium: Trace wear metal

Apologies if the data is hard to read the board doesn't seem to accept tables. (or maybe its me)

Sample No1

Elemental-----------PPM------------Chemistry

Aluminium 43 % Water 0
Cadmium 0 Boron 147
Chromium 0 Silicone 19
Copper 100 Sodium 10
FW Index 17 Water Content 0
Iron 266 Lead 0
Barium 1
Nickel 0 Calcium 581
Silver 0 Lithium 2
Tin 5 Magnesium 2
Vanadium 0 Manganese 2
Manganese 0 Molybdenum 0
Titanium 0 Phosphorus 491
Zinc 8 Potassium 7
Total Acid 2.3
Viscosity at 40’C 23

Tech Data Sheet for ZF8 shows Viscosity of 26 at 40’C
Boron used as an anti-wear agent.
Silicone used as Antifoam.
Sodium? Probs shouldn’t be any.
Water shouldn’t be any and wasn’t.
Calcium used as dispersant/suspending agent/detergent.
Phosphorus used as anti-wear/extreme pressure agent.
Potassium? As Sodium.
Total Acid? Hope it’s not the pH!
Zinc anti-wear or out of a bearing?

The form of the detected metals isn’t stated. I presume they’re in elemental form rather than oxides/salts/etc.

Copper looks high, no idea how many bronze bushings in there. Guessing the cooler matrix is aluminium along with the housings. The iron? Probably from the pressure plates, bands and discs.

The report flagged up the wear section in RED I’ve no idea if the above results are good or bad after 60K on factory fill oil - the car still drives brilliantly.

Was it worth changing the oil? Initially the car wasn’t happy but soon settled down, but that was a surprise. What upset it with clean oil I can only speculate. Perhaps the suspended crud didn’t flow through tiny galleries so well? That said its viscosity was only marginally degraded.

So much rubbish and mis information touted & spouted on the web about these gearboxes.

[Metrics]

Interesting write up John.

Trouble is it's pretty much impossible to know if the analysis that's come back is normal or not. The only way would be know what it's looked like at say 20k miles, then 40k miles and then 60k miles.

But there's also a risk of overthinking about these things. Enjoy the car, change the oil at the right intervals based on an engineering vs accountants approach, and the car will give plenty of reliable miles.

My only suggestion would be have an oil change that flushes through all the oil, rather than just drains and leaves a fair chunk in the 'box.

In terms of the initial miles where you got abruptness and hesitation - I suspect this is the adaptations being reset through the refill process when connected to the computer? Just my guess.

[JohnW]

I had the gearbox oil changed at 85k, a little bit late, but the changes on the whole feel smoother, with less of the occasional jolt. Also in Drive (not Sport) it tends to hold in second more when rolling slowly in a queue or if not stationary for long.

Not as important, but I asked the same garage about the diff oil, they virtually refused to change it, saying it’s not worth it, so I reluctantly (I’m waiting for a hip replacement) sourced a cheap oil extraction pump and some Castrol diff oil and did the swap myself with a new plug at 100k. I managed to extract around 90% of it with the £15 12v Chinese pump, so quite pleased.

In the end the replacement plug wasn’t really needed, but the oil I extracted was cloudy and grey a little suggesting a bit of water ingress.

I’m glad I had the gearbox oil changed and diff done myself if anything for piece of mind. I need to rub down the diff casing and give it a coat of chassis black now.