ZF tranny info

[greenjag03]

Hi all
Wanted to get this info on the net, hopefully it'll help others with the ZF 6HP26 transmission on Jags.
Also affects some Aston Martin, at least one Hyundai, and a few BMW as well.

Issue: sealed for life tranny leaks from composite sump - gasket failure. Cheap nasty fasteners made of cheese have a head size not commensurate with the tiny torx recess. They're also ordinary steel and the casting boss these things screw into are open holes. Lovely little reservoir for all that salty road water. You can guess what happens when attempt is made to remove these pathetic screws. Plain steel screws into aluminium with a dosing of salt water is not sound engineering practise.

Jaguar wanted £700 + to do the job, but much of this is the con trick price of ZF fluid.

I've done mine myself using a 4mm drill and an SKF stud extractor to get the old screws out.

Replace the screws with M6 x 30 stainless socket cap heads and washers. Also fill the top of the hole with waxoyl.

As for the fluid - don't let them BS you that your tranny will fail if anything other than ZF golden elixir is used - it's actually Mercon 5 and you can do a fill for about £30. In fact in some countries Mercon is specified for this box.

Filling presents problems since the fill point is on the side of the box with not much clearance - so no gravity filling here. I spent £12 on a small fuel rated bilge pump at a local Chandlers and it included pipes - best £12 I ever spent.

All in all I've dropped the sump, replaced the gasket, replaced the fasteners with cap head stainless which is what should have been used in the first place, and done a complete refill for about £50. Box runs perfectly.

This was a major issue a while ago with Jag and BMW owners as no one seemed to know what the alternative was for ZF ransom oil, and how to get the old screws out.

So save yourself over £600 - stud extractor, fuel rated small boat bilge pump, M6 x 30 stainless cap heads, Mercon 5 fluid - jobs a good un.

Hopefully this would help anyone with a leaking 6HP26 tranny sump who might be fooled into thinking they have to pay the ransom.

Edited by greenjag03 on Saturday 21st October 21:28

[greenjag03]

If your box is a ZF 6HP26 then yes.
In some countries Jaguar actually specifies Ford Mercon 5, or Mercon SP for cars fitted with this box but in europe they don't want you to know that.

Ford owned Jaguar when these trannies were chosen for the S type, and to my knowledge others using a 6HP26 included Aston Martin, Hyundai, BMW, Some Range Rovers - and indeed some Audi's.

It's a serious problem common to all makes - they all eventually leak and use self oxidising crap-co nasty trick fasteners to hold the sump pan on.

There was rumour than some Jag owners were going to Hyundai and getting ZF Lifeguard fluid at non-Jaguar prices.

All to do with making as much profit as possible. Remember these transmissions take about 9 litres of the stuff, and Jaguar quoted me £270 inc vat for a fill. Works out at £30 per litre, daylight robbery.

As it happens £30 - £40 buys you 2 x 5L cans of Mercon 5 or SP if you shop around. No brainer.

Best way for sure is to get under your Audi and see what it says on the transmission sump.

Check this out: audiworld.com and find the following discussion, very interesting indeed - 'Automatic Transmission Fluid (ZFLifegaurd6=Ford Mercon SP)'

Also remember that the filler point probably won't have a lot of room around it. You need a pump to get new fluid in.

[greenjag03]

dcb said:

Good info.

Time to pester Jaguar, Aston Martin, Hyundai and BMW or maybe go upstream and take it straight to ZF and
get them to nag their customers ?

Anyone from ZF tech dept reading ?

Think its been tried already, excuse was always the same ----"it's a sealed for life unit" Which of course it is'nt,

Its got drain and filler plugs. But no one got anywhere with these criminals.

Personally I favour either of the following: 1) tech signatory at Jaguar who approved this tranny gets to eat the old screws from mine, or 2)...person at ZF responsible for selecting them in the design gets to eat them.

....But then I'm old school and served my apprenticeship when I was a lad with awareness that mistakes usually involved pain.

For me the PITA was the screws, cheap nasty muck, basically. As fitted to Jaguar, Aston Martin etc :-)

[greenjag03]

Max_Torque said:

How old was your car?

It's an 03.

However, personally I don't see age as a mitigation for bad engineering practice, and it's astounding how this one example has caused so much expense and grief to many.

If you got one of these boxes run your finger over the top of the casting where a fixing screw goes----see how it's open to road water. No wonder the screws corrode, but then they wouldn't if they were stainless.

I do wonder how many cars were either scrapped off or owners got conned into replacement transmissions, when the problem was nothing more than a fluid leak.

My Jag started to kick like a mule on shift changes, reason: low fluid. So you can see how some might be conned as the kick when it's struggling for fluid pressure really is vicious and could be mistaken for a tranny on the way out. Less than honest dealers love this kind of thing.

Other than that to be fair, these boxes are pretty solid, mine's back as smooth as when it was made.

But like I say for me the criminal act was the use of plain steel fasteners with a designed-in salt water reservoir.

Though the box shouldn't leak in the first place, of course.

[greenjag03]

annodomini2 said:

Mine is the 6HP19A which is a variant of the 6HP26

There is mention on Audi forums about this. Consensus being that your fluid probably is Ford Mercon, or Shell equivalent.

Might be wrong but think 6HP denotes six speed, and 19A might be ratios, power loading etc.....but yes yours is a derivative of the series.

Check out forums on audiworld.com, someone took the time to post a very good analysis of the fluids used.

[greenjag03]

227bhp said:

Stainless steel is much more liable to cause galvanic corrosion than the steel was.

Especially so what with the Stainless readily oxidising, which is why it's also called inox / rust free etc. Guess this is why they use stainless for marine fittings.

[greenjag03]

jjohnson23 said:

Have a look at this.
http://www.bssa.org.uk/topics.php?article=89
Found it useful a while ago.

Intertesting. Owning dozens of bikes over the years especially ridden in winter I never saw corrosion on stainless fasteners.

[greenjag03]

Max_Torque said:

.... The original engineering is perfectly fit for it's purpose / design life.

Mine wasn't.

[greenjag03]

Max_Torque said:

Sure, they could have used stainless setscrews, (if we assume for a moment that would have fixed the issue)

Actually it wouldn't have fixed the issue....a set screw doesn't have a head, so clearly wouldn't hold the sump pan on.

[greenjag03]

GreenV8S said:

Just my thought. If it's screwed into aluminium, you might not want to be using stainless fasteners. Passivated non-stainless steel would probably be a better bet.

Depends what the passivation is. If it's Zn then you'd get an instant battery soon as any salt got on it. Cr is what defines Stainless. Cr doesn't rust / oxidise.

The original fasteners are just cheap Zn passivated, hence the corrosion.

However the corrosion isn't the main issue. It's the fact that the screws were soft as cheese with a ridiculously small torx diameter. I read somewhere that ZF did increase the torx size after some complaints.

And also the fact that sealed for life isn't, not when the gasket's got a hole in it.

It's just a fine example of what would otherwise be a well designed drivetrain item let down by penny pinching most likely. In every other respect these boxes are damn good.

Edited by greenjag03 on Monday 23 October 19:34

[greenjag03]

Max_Torque said:

And 03 car is getting on for 15 years old. Cars are designed for 10 years and 150k miles.

No excuse. Bad engineering by ZF when it was new is still bad engineering when it's 15 years old.

I like my 03 S type 3.0L SE. Sure I could buy another later model, but I like this particular one for personal reasons. It's my fourth Jag and will be my last, probably outliving me.

Edited by greenjag03 on Thursday 26th October 17:03

[greenjag03]

eliot said:

I take a pot of copperslip to the tyre place and get them to put a dab on the threads and hub face - they told me that nobody does it (apart from staff)

I had a mate once who had front pads done at a tyre place, they put too much copper-ease on his hubs which got to the discs, not nice.

Putting that stuff on steel to steel threads like wheel studs is fine, but personally I've found it seems to dry to a cack when used on steel - aluminium. Don't know why

Edited by greenjag03 on Monday 23 October 22:30

Edited by greenjag03 on Monday 23 October 22:33

[greenjag03]

Max_Torque said:

it's not "bad" engineering.

Engineering is a compromise, between cost, capability and durability.

You cannot have all three.

ZF made an engineering decision, probably based on objective test data (like salt spray tests) that told them the fastener system used was sufficient to last the design life of the car. And they were right, it did.

Thank you for suggesting it was deliberate.

Though I might suggest you're missing the point slightly - what defines the design life in an example like this? is it the self-corroding fasteners, or the fact that the sealed for life box leaks at some random time ? Yes, many a ZF 6 leaked during warranty.

As for cost capability and durability, I also have a 15 yo Suzuki Swift with more mileage than the Jag, which I've had from new. So far in 15 years all it's ever needed was tyres, oil, brakes, plugs, distributor cap, wipers, a couple of track rod ends, and the occasional bulb. It's only a 1L 3-pot runabout but by heck you couldn't get an easier car to service, and no dirty design life tricks anywhere. Also runs on a whiff of petrol :-)

On the other hand I have a Mercedes van, guess what----the gearbox synchro's kaput. Not really bothered to look as van SORN, but wouldn't be surprised if that box is made by ZF as well. Shame as it's still got a cracking engine after 176,000 miles.

So, to a point I have to agree with you, however my sentiment would be along the lines of perhaps this day and age big business is using factored 'design life' as a price we pay for luxury / hi tech products.

Brings to mind a well documented comment made by a certain CEO of a very big software company....."don't give 'em what they want cos they won't come back and buy another one".

Mugs aint we. Though I maintain old stuff that keeps on going is better than new stuff which dies when someone else says it dies.

Thank you for a stimulating exchange of sentiment.
Regards

[greenjag03]

helix402 said:

I serviced an 8 speed ZF box with a ZF kit. It came with new modified sump bolts, can’t remember what material they were.

They'd be zinc passivated steel, just like the originals, but with larger torx drive. It was the only acknowledgement ZF ever gave to the problem.

[greenjag03]

It's fixable... said:

The thing to remember about any galvanic couple ie any metal to metal interface is that the less noble material will rot first.

As other posters have stated ali to stainless is a "worse" galvanic couple where the ali is most likely to corrode.

Ali to passivated steel is also bad but the ali will corrode slower.

Copperslip can be bad as it can cause additional acids to be generated depending on the salinity of the water sluicing the interface between metals.

Look up sacrificial anodes on the interporn to better understand the concept.

Thanks for that info, but, I'm sticking with stainless with a good dosing of waxoyl. It worked for me on bikes ridden through numerous winters over a 30 year period....never got a corroded fastener.

Re passivated steel: I suspect galvanic action between the fastener and casing is largely dependent on what the fastener is passivated with i.e. Zn, Cd etc. I suppose in effect you could say stainless is passivated with chromium...which doesn't rust. Then again I always coat threads on weather exposed parts with waxoyl, so I guess I'm keeping the electrolyte i.e. salty road water out. perhaps this is why I don't get corroded fasteners.

Copper-eaze / slip........yeah can't stand the stuff, shouldn't really be needed.
Cheers

Edited by greenjag03 on Thursday 26th October 17:01

[greenjag03]

As a point of interest, I once heard the Japanese don't salt their roads. Maybe thats why an MX5 I had a few years ago exponentially rotted out on me big time.

Salty water makes a good electrolyte.