Valve body replace, easy?
 

2002 Audi S8 D2 86000mls

Hello all

I have owned the above car for about 8 months and am spending a small fortune in trying to make it the best it can be (for a 15 year old car). I have already done lots to the car, new front susspension links, front brake pads and discs, new catt on one side, water ingress sorted, gearbox output shaft oil leak sorted etc, etc. I am now thinking about some preventative maintenance for the gearbox. I have changed the gearbox oil and strainer, to be fair, the previous owner told me that it had been done previously 20,000 mls ago. The oil actuall looked pretty good and I could see evidence that some one had at least had the pan off at some point. So to my question. Would you guys recomend preventative valve body work? the car has absolutley no gearbox issues at this point, well none that I can pick up on anyhow. I have an official version of VCDS and there are no transmission codes. All is good.

Would you?
leave well alone?
Remove the front lower valve body to have the pressure regulator valve upgraded (aprox £350) with new valve body?
Replace the whole valve body assy for a new genuine part (aprox £1200)?

I am prefering the latter as clearly this will also incl new springs, seals, stariners, dampers, solenoids etc. What do you guys think? is swapping a complete valve body whilst the tranny is still in the car as easy as it looks? If I go just for the lower front valve body only, can this be removed whilst leaving the rest of the valve body still in place?

Any help / points to other threads much appreciated.

Would you consider a big road trip/short holiday and take it to ZF in Germany ?
It sounds mad but they seem to offer a fantastic service.
Lots of positive reviews if you google "zf dortmund gearbox service"

Sounds like a long way to go. I'm looking more for a diy solution. I bought the car originally as a hobby and enjoy doing the work myself. It really hurts when I have to take the car to another mechanic. Clearly I would have to do so if the gearbox needed a rebuild. This would be way out of my comfort zone but in terms of doing something preventative, I think I would like to do it myself. I get a great feeling when I manage to fix / improve something myself

Minor point, but this is in the D3 section.......

Assuming you are talking about a D2 the valve body doesn't seem to crop up much as an issue, so apart from the usual preventive ATF/filter change why touch it?

OK, fairly new to the whole forum thing and not sure how it ended up in the D3 section. I thought I posted in the D2

Any advice from long term D2 S8 owners would be very welcome and please correct me if I am wrong. I understand that these 5hp24A gearboxs are prone to A clutch drum failure caused by pressure spikes which in turn is caused by valve body wear. Searching the net, this seems like quite a common problem. Is this not the case?

The early ones are. The later ones like the FBG in your 2002 seem to be more affected by the A-drum roller bearing collapsing which then causes the clutch pack to slip and shreds an o-ring which releases line pressure causing all the other clutches to also slip.

Changing the valve body is simple if you are meticulous about detail and cleanliness although its a very messy job in the car since it holds a lot of oil which will drop on you :D I would argue though that if its shifting ok then changing it is a waste of money. The best preventive maintenance on it is to change the bearing, but that's inside the box behind the oil pump so is a considerably bigger job. Still, its pretty obvious when that bearing has failed (clutches slipping) and if you get to it immediately it won't do any lasting damage.

Treat it to a new MAF if you haven't already - that has a surprising impact on the gearbox behaviour and longevity :)

I'll ask a mod to move the thread to the D2 section for you :)

Already moved! +++

Thanks for the advice. Why is it that a MAF sensor will have such a big impact on the gearbox. I have a reasonable knowledge of car ecu control systems and components but just thinking about it I can't get my head around why it should be. I understand that MAF sensors get sluggish with age. They measure air volume and mass entering the engine. If sluggish you can get an incorrect reading and this a weak or rich fuel mixture. This will though be picked up by the O2 sensors and the fuel trims altered to bring back to spec.

I'm sure you are right with what you say as I know engine management systems and components do all kinds of less obvious stuff. If you could help me understand I would much appreciate it, just for my future knowledge.

Thanks

I have scanned through quite a few different forms and it does seem a common opinion that the MAF sensor will inpact shift quality and timing. As I said in my first post, I don't have any transmission issues but I do believe in preventative maintenance. The transmission is by far one of the most expensive things that can go wrong and so justifies some preventative expense. I do more research and will let you know where I go with this.

Just as a side note, I also plan to change the timing chains and adjusters next spring. Also a preventative measure.

The ECU measures (or estimates) torque loading on the engine using the MAF and then uses this information along with the TCU to optimise shifts.

If your MAF is past it, you can get some very rough shifting on moderate to heavy throttle.

Mine threw a code right on max rpm on the highway one day.
It banged into 3rd gear and I thought I'd broken something.
Gave me ESP and ABS fault lights - I thought the ESP might have chucked a wobbly!
Only on running a scan did I spot the faulty MAF.
Replaced it and everything got better!