[D2 S8/A8] Question about rebuilding things and the idiosyncrasies on an '02 S8

[preheated-ocean]

Hey,

Few questions - I'm new to owning an S8 and love the thing. But have a few questions about replacing/repairing/rebuilding certain things on the car

Steering/Suspension:

• I know there are service kits for them, at least I see a lot around when looking it up, but I am curious to know if anyone here has successfully rebuilt one of the power steering racks that are fitted to the S8. What was it like, would you recommend it, did you use a service manual or go at it with self documentation, (if yes to using a manual) where did you get it at/from?
• Does anyone have or know how the variable steering system works? Can it be adjusted through tuning?
• Has anyone installed polyurethane bushings on the suspension? PowerFlex offers these and wasn't sure if anyone has experience with them on the D2. I've used the same make on other cars.

Engine/Transmission:

• The RPMs waver at ~2000 in 5th gear while cruising at 50mph with light throttle (enough to maintain speed on flat ground). The car shifts fine(ish) (3rd to 4th is smooth but very noticeable), and above 50 seems very steady. Would this wavering be caused by the TC or is this a gearbox issue? I was told it was rebuilt by ZF within the last 10 years and has less than 40k miles on the box.
• Has anyone rebuilt/refreshed the valve body? Car is reading close to 160k miles on the dash and it may be nice to give it a refresher.
• What exactly does ZF replace/rebuild on their transmission services/refurbed units? Clutches, gears, valve body, pump, etc.
• Like mentioned above, RPMs waver at ~2000rpm - could this be caused by the secondary runners in the intake opening/closing when they shouldn't be? Its pretty noticeable feeling and have no way of logging that (unless someone can tell me that would be sick). Maybe by using the maf?
• After a normal drive/commute (20-30 miles) when the car is put into reverse there is sound coming from inside the car that sounds like a muffled bottle of rocks being thrown around. You cannot hear it from outside the car, but only the inside. Could this be the TC? Engine or Transmission mouts? Something normal?
• Using VCDS how can I monitor/log TC activity, Trans oil temp, and anything else I should be looking at? Just need the group numbers.

The car has no CEL and checking with VCDS there is no codes anywhere related to engine, transmission, steering, or suspension. I love this car and its been beyond impressive until within the past few months. I am slowly loosing confidence in driving it and I feel I am slowly turning into an old insane man who fancies a tin-foil hat. I just (like 40 minutes ago before posting this) logged the Absolute Throttle Position, RPM, MAF, and load. Hopefully that will lead to something.

Any response related to what I asked is great. I want to enjoy this car as much as I can and right now every drive has been radio off and freaking out over every little thing. Mind you I own a built S4, and I have more confidence in taking that on a 1000mile road trip than I do with this here S8, so I am well aware of the life that comes with owning this era of Audi.

[Black Jack]

Hey P-O - As someone currently in a rebuild of a D2 S8 - and as you say, "...comes with owning this era of Audi" - I'd simply assume: everything's wrong. I haven't come across a single component so far that I would consider to be in operational condition. I'm going to send my rack for rebuild somewhere local, likewise to take a look at the transmission, I'm going to get every power steering and A/C hose line rebuilt, all the gaskets are beyond their lifespan, hardware is corroded, bushings are on a case-by-case basis.

My problems are not necessarily your problems but what you're experiencing is likely the topside of an iceberg. This isn't the answer you were searching for, but you're going to just need to dig in and find out most of it for yourself. And look on forums with more European participants.

[preheated-ocean]

Thanks for the response! Fair point and I guess this is what I, and many others, kinda sign up for when getting into these cars. It may not be the thing I want to hear, but hearing it is still good. Misery loves company and I’ll end up where you are some day - rebuilding one of these. Not gonna lie, I was also having a smidge of a freakout because I had 5 cars take a shit within the past month. The hobby is fun when everything is working as it should be. I’ve also been cruising as many forums as possible for write ups and cross referencing things with one another to find whats more informative and what is actually talking about the post-face lift S8 vs. pre-face lift. Trying to make a library of it all.

Anyway, a few things I found out about my car that solved a lot of concerns. Got a couple other opinions on the car by letting others who are more familiar drive it for a few days.

- The throttle wavering is not the transmission, or TC, or engine, but is/might be the tune that is on the car. Its believed it is hitting a grey area and thus causing it to move the throttle around slightly. Under load and coasting the car is fine. Now time to log some more tables..
- some of the goofy shifting is just conditional/nothing to be concerned about.
- the rattle in reverse was just heat-shield that had worked its was loose.
- the car was completely out of alignment by a lot in all 4 corners. Everything was adjusted and torque on all components were checked and verified. Car drives true and no more horrible road noise
- wheels were also road forced balanced, which helped smooth a lot of things out/make everything behave a tone better
- Steering is normal.

All in all, we all good for now. I did find out the proper group numbers for logging the transmission and TC. Still haven’t found much about the poly bushings, but maybe thats just something I should take a dive on? Currently bushings are a-ok so I’ll at least wait until those are toast. Idk, we’ll see.