Another D2 S8 with Auto Transmission problems

[SyncroS8]

I wanted to go as far as I could to check for any other problems.

So I removed a couple of circlips which hold in a spring...which holds in some rubber seals onto the next housing.





I managed to get the housing out. All looks good.



You have no idea how many clutch packs are inside this little lot!



Epicyclic gears...

I removed this heavy set of gears but couldn't pull the next section out and wasn't prepared to try too hard without pulling everything off the back of the gearbox (torsen housing etc) so it went back in.

I didn't find any issues with the clutch packs or gears so put it back as it was and I'll just deal with the obvious issues.

I'll be ordering parts from Chester Transmission on Tuesday.

I hope that this has given you all some idea of what's inside one of these gearboxes and just what's involved in fixing one.

I've seen two A8s on ebay over the last two days for around £500. Very tempting but I don't fancy doing this every day of the week!

MG

[47p2]

A massive task to take on, interesting to see the inside of these boxes.

There is a chap on a couple of Range Rover forums who seems to be a bit of an authority on these boxes, RRPhil is his user name and he's in Blackburn, I'm sure if you were stuck he would be able to help you with any questions you have, he is very approachable .

[sarg]

Loving this thread, top work Syncro

I know my brother was tempted to do something like this when the box went in my QS, but we simply didn't have the tools or facilities to do it - brother always said it was probably a single cheap part inside causing the problem.

However, I am curious, would this broken O ring really cause the box the stop working all on its own?

[PsYcHe]

Yep... It causes oil to leak past, pressure drops, and box can't function on that clutch pack.

Pretty poor design... But if you also consider it was an O-ring failure that caused the Challenger disaster.. that's how important these things are.

[SyncroS8]

My understanding is that oil pressure controls how much slip the plates have. With the drums out of the box, each set can be moved by hand quite easily. This is the opposite of an LSD where you clamp the discs in.

With the O-ring allowing the oil to flow elsewhere, oil pressure is lost in the correct places... Hence more slip.

When driving, 1st to 4th gears would initially engage, then slip. My guess is that when the solenoid operated, the flow of oil would engage the gear but then with the oil pressure loss, you get the equivalent of neutral.

The bearing dying has allowed the drum to move too far forwards hence the scoring.

I could be talking rubbish though

MG

[sarg]

Thanks for that MG, we're pretty sure now that mine almost certainly had the same problem, symptoms seems very similar, plus the fact that it was a sudden failure, not a gradual thing like I guess it would be if the clutches themselves were worn out.

However, mine failed within days of having the gearbox oil flushed and replaced, do you think this was coincedence or could the oil flush have broken the O ring, or somehow dislodged it?

[SyncroS8]

That's fairly difficult to say. It could have been coincidence.

I've never seen sludge inside the gearbox... only in the sump but then I've not stripped down a gearbox that has done 200,000 miles without an oil change!

I personally would have no hesitation in changing the oil so long as it's done properly.

Get it wrong and you can do serious damage.

The O-ring design is horrible and I'm surprised that ZF have designed a gearbox that can fail so dramatically from one O-ring failure. Maybe they could have designed it better so that the O-ring was more supported, maybe they should have used better material for the rubber... I'm no engineer. I think if ZF were revisiting this now, they'd probably re-design it with a bigger O-ring and re-machine everything accordingly.

Oil changes are good. I would say that 60 or 80k for an auto gearbox oil and filter change is a good idea. I think maybe the same time as the timing belt would do but that's just my opinion.

Here's a diagram from ETOS with the parts that I need highlighted in red.



From Audi, you can't buy the drum separately. I'm hoping that you can from ZF (therefore Chester Transmissions). Finding the O-ring on the parts page is a nightmare as VW/Audi have just put all of the O-rings on one diagram... with no clue really as to where they go!

MG

[Conan_the_Librarian]

Top thread, added to sticky. Do you know the ZF catalogue is here?

CtL

[SyncroS8]

Thanks Conan,

I couldn't get the ZF Online system to bring up any individual ZF transmission parts.

It looks like the closest ZF supplier to me is Auto Supplies Ltd in Kidderminster.

I am set to get parts from Chester Transmissions but from the lack of response, I'm guessing that they're mega busy.

I did find the link to the ZF parts catalogue very useful though and have got the following part numbers for the bits that I need.

Drum: 1058 271 041
O-Ring: 0734 313 151
Bearing: 1058 202 016 (Audi part no: 01L 321 157A £6.06)
Rear flange seal: 0734 319 588
Left flange seal: 0734 319 419
Right flange seal: 0734 310 342
Bolt cover caps: 0501 314 585
Sump gasket: 1058 303 015 (Audi part no: 01L 321 371 £19.19)

I have the prices for joe bloggs from ETOS for some of the parts. We'll see how ZF compare.

I'll put the prices up as they come in.

I looked up the oil when I first got the car and found that Dextron VI is the correct spec for the gearbox. I know that this is a widely discussed issue but as Chester Transmissions use this is all of their ZF 5HP24A geaboxes and it's the correct spec, I'll be using it too. GSF is around £30 for 4 litres.

MG

[SyncroS8]

I've found some american sites with some parts with prices.

http://www.thectsc.com/

http://www.latransparts.com/store.php?crn=43

It looks like my drum shouldn't be as expensive as first thought, although that's in $ so I expect that the price will jump a little.

MG