So we're into the trouble parts!
On reading up on the ZF 5HP24 gearbox (ours is the ZF 5HP24A), it's used in the BMW X5, BMW 840, 740, 540, Z8 Range Rover (the BMW one), lots of Jags and quite a few Audis!
If you type in searches to Google, you'll find lots of them with gearbox problems.
The ones which keep popping up are 'Clutch pack A' faults and 'Reverse gear' faults.
The Clutch pack A controls 1st to 4th gears. The drum which holds the discs has a weakness where the circlip sits.
This is NOT a regular fault on Audis. The reverse gear fault is evident on Audis. The fault is due to a 'crumbling F clutch'.
This F clutch is buried right at the back of the gearbox and goes in first when build it. Thankfully... my reverse gear works very well
I've only found this out through the internet. I think my wife thinks that I've losing my marbles spending so much time looking at gearbox parts
So out with the first section.
Remove the large circlip and everything is accessible.
This is where inspection is key. You're looking for anything which is scored, has changed colour (blue tinge etc), O-rings, the hubs and discs.
I took a lot of photos just so I know how everything goes back together.
Clutch pack inspection time.
Then the culprit was found.
This one O-ring (well documented as failing on other ZF 5HP24 gearboxes) is the cause of all the problems.
More inspections...
The bearing in the photo below... fits in there!
In fact it's dead. I managed to find all the rollers (fairly important inside a gearbox!)
I would put this down to a lack of oil pressure but the gearbox has done 180K.
Now the drum..
Score marks are evident.
There has been a little bit of metal going through here.
Ok, so we need an O-ring, a Drum, a bearing...
Onto the next section.
MG