I'm sure this must be gearbox, but what to do?

[HPsauce]

OK, maybe I'm being dumb, but where is the latency setting?
The VCDS Test came up latency poor, but none of the settings appear to be that.
Or is it a Windows (device manager?) setting, in which case i can't find it in W7...

Edit: found it, see next post - very strange.....

[HPsauce]

Well that's a bit odd, but it's working - thanks.

For some reason the serial port wasn't showing in Device Manager while conected in the car.

But when I booted up in my house and plugged the lead in I could see it and get into the Advanced settings and change the latency.

I marched outside, plugged it in, Tested good and found lots of controllers.

Not got time now, but I'll run a full scan later and see what I find. There's nothing gearbox-related though (I did press the pedal!) so I'll post elsewhere for advice. There are definitely a few codes showing.

[HPsauce]

Originally Posted by HPsauce

There are definitely a few codes showing.

Nothing exciting though, all related to locking/alarm and I can explain them all apart from one suggesting a possible leak related to the pump.
As it's always taken the same time to lock/unlock I'll ignore that for now (at my peril!).

[HPsauce]

Originally Posted by SyncroS8

If it's on a direction change, then it's more likely to be a diff related problem.

I would check the levels of the front and centre diffs as they have different oil chambers to the autobox and run different oil.

Well, I haven't had time to investigate yet, but today I was talking to one of my neighbours while I was investigating some problems on his business admin PC. He's been away for a month but runs a specialist Mercedes repair shop, customers with cars worth up to half a million quid!

Anyway I mentioned the symptoms and your thoughts and he was VERY much in agreement that should be investigated first. So I'll get on it ASAP.

Edit: Went round to my local (newly-discovered) independent that reckons they're all ex-Audi techs. Had a good long chat with the boss.
Certainly seemed to know his stuff, made various suggestions including the diffs (and knew which fluids went where), but said without "seeing it in action" he was obviously guessing. Also suggested a gearbox fluid & filter change which they can do.
So, booked in for an "investigation" up on the ramp while I wait & watch a week on Monday (11th).

[HPsauce]

Well, there's nothing wrong with the diffs at all. Just a very tiny "seep" from the rear one of no consequence.

So it's booked in for a "kill or cure" fluid and filter change in a couple of weeks time.

[HPsauce]

Well the box has survived a 2000-mile round trip covering all sorts of road conditions:
Hacking along motorways and the like - easy, peasy mostly sitting in 5th.
The A9 and similar roads - a fair bit of dropping 2 cogs into 3rd and heading towards the rev limiter past big trucks and rows of the "less able".
Tiny single-track wiggly roads.

Been using "manual" mode a fair bit, mainly to keep the revs down when pottering on the little roads. Only had a couple of "events", one of which was a serious judder going up a VERY steep twisty hill in 2nd gear, so ESP may have been contributing.

Going in on Thursday for a fluid and filter change. Fingers crossed.

[HPsauce]

What a transformation!
I think in all they used 6 litres of gearbox fluid (of 9 they got in just in case), so not a full flush, just a drain & refill.
But as soon as I drove off I could tell it was much much better. Smoother, quieter, right from the first yard.
Drove around about 15 miles giving it a "good thrashing" in both auto and tip modes and it was as smooth as silk.

I also got them to delve into the ECU box and fit the cruise control ECU that I bought from A8parts recently; apparently it involved taking EVERYTHING out so I'm glad I didn't decide to tackle it myself!

That works too, so I'm a very happy bunny.

[Adrian E]

Good to hear

Did they measure how much fluid came out? It's always an interesting piece of info

Mine took 8 litres when it was re-filled after a filter change, but might be that the box is slightly different seeing as mine's a late one?

[HPsauce]

I didn't ask and they didn't volunteer the info.

After my "test drive" I had to visit someone literally over the road from the garage and as they were still open I popped back in to say how pleased I was.

The owner and the techie who did most of the work said that what came out was pretty black and the filter was filthy. They suggested doing it again in maybe 50,000 miles more if I was keeping the car.

I said I'd see how it behaves, but probably do it again at the next major service (or earlier) as a precaution and because there would still be a fair proportion of crud inside even now as only about 2/3rds of the old fluid was removed. They said if I did it soon the filter would probably not need replacing and that and the associated gasket were about as much as the fluid so a fair saving.

The owner did also say that the fluid for the latest (8-speed?) gearboxes was twice the price!

[HPsauce]

Hmmm..................................

Did a fair bit of driving over last weekend and whilst generally MUCH better it did still have the odd "moment".

One in particular was noticeable; I was doing at most 20mph turning right around a very large (sized for artics) empty roundabout on a backwater road (Industrial estate shortcut on Sunday lunchtime, so deserted).
As I started to turn left to exit it juddered a few times as if changing it's mind about what gear (2nd or 3rd I'd guess) then settled down OK.
I was driving VERY sedately as I had a frail 93-year-old passenger in the back!

The centre (Torsen) diff has had its oil replaced, but the rear one hasn't (drain plug in too tight) so not sure if that might be relevant.

Just wondering if the gearbox ECU might be suspect; if so are they swappable or do they need recoding?

I do know (think I mentioned this before) that my car has had a "chip" replaced ("Superchips" early in life, before me) to remove the 250kph limit and allegedly adjust the midrange gearchange points - would that be in the gearbox or engine ECU. It was only 1 chip as I have the original.
As I have never, and will never, exceed 250k in this car I'm very happy to revert to "S8 standard".

Further thoughts anyone?

Also can anyone outline or explain how the gearbox and ECU interact, i.e. what measures and decides what and how changes are controlled, as I believe there are some electronics inside the box itself - or are they just sensors and actuators?