Another sad S8 owner because of the gearbox
 

So the S8 flew through it's MOT after two years off the road, but I have the classic gearbox problem.

I took the car for a drive last night and there was a little slippage, but today after the MOT big slippage, bangs and PRNDS.

Turning the car off and on resets the PRNDS, but the slippage and bangs are back.

The car, at first, doesn't seem to engage and then I get the bang, and Reverse works just fine and doesn't set off the bangs.

My mechanic who seems very competant and is an Audi specialist (and who is now on holiday for 3 weeks, spending all the money I have given him) changed the oil, but didn't leave the transmission to drain, and could only warm the gearbox using idle: I know that's not the full reccomended process.

I think my options are:

1. Have the transmission drained overnight and refilled as per audipages by an audi specialistgarage to see if that fixes the problem
2. Assume the gearbox is terminal and get it serviced by a ZF specialist: but how much?
3. As 2. above and get it serviced by the guy who does it free, but where do I find his details?
4. As 2. but get a replacement from A8 parts, take the risk that its secondhand and get the original refurbed if needed at a later date either paid or free.

At the moment I'm thinking of 1 then 4: any thoughts?

If I drive the car in limp home mode will that cause any problems>

Doing the oil change the correct way won't hurt, worth a try. Many a tranny has been brought back to normal operation, after an oil and filter change.

I'm not waiting for mine to let go, I'm doing an 01E 6-speed manual conversion.

I reckoned it wouldn't hurt as well: can I damage the transmission by using it in limp mode?

Much depends on what the issues are. If the oil is filthy dirty, and mixed with fine aluminium particles, it won't do the internals much good.

I would not drive it, or keep driving to a minimum, if you have to use her at all.

I forgot to ask - what's the current mileage on your S8?

It's done around 120K: I ran the car this morning and was OK for 5 miles then it was back to limp mode.

I just tried it at lunch time and it went into limp mode straight away.

So I understand you recently have oil changed. If that is the case then usually it is because:
1. wrong oil was used
2. oil level is not correct
3. fresh oil has lifted up gunk that have settled down with old oil and blocked filters or causing sicking valves
Response to your options:

1.If correct oil was used then another oil change will not cure problem and as oil is quite expensive I would not go that way, just check the level and confirm with mechanic that correct oil were used.

2. It might not be terminal but if there is gunk that was lifted up blocking filters or valves it will require stripping down and cleaning, which would be quite costly so might as well do a full rebuild unless you are doing it yourself.

3. If you can find that guy it is a good option depending how far he lives or what the postage costs would be there and back.

4. Probably no unless you can get gearbox that was recently rebuild and still come with warranty. That will set you back roughly £300-700 for the box, £100 for the oil, £30 for the filter+gaskets and £200-250 for the job and might fail in near future. If you can get one that was rebuild recently then it could very well be the option. I had a chance to buy one which had done only 2000 miles since supplied by dealer for £450, I was considering to give £400 offer for it but decided to do manual conversion if mine ever fails, and that one is gone now.

Do not drive if it is slipping clutches , you will burn them out very soon and the it will definitely require rebuild.

120K for an S8 is a good innings to be honest, and add to that I've never seen a box recover from limp mode with anything less than full rebuild....

True, if its very recently been 'serviced' incorrectly, and you can undo those errors immediately without casuing permanent damage, you're in with a chance, but frankly, it doesnt look good....

Either way, dont take it to an Audi specialist for an oil change. Very few of them really know much about autos as they are supposed to be sealed for life in the eyes of Audi.

If you think there might be signs of like, take it to a ZF transmission specialist, they will really know what they are talking about. Its the same box (and problems) that come in BMW's, Range rovers etc....

Isn't the guy that offers free rebuilds in the US? Or is there someone else that'll rebuild for fun?

Before my S8, I had an A4 3,0 Avant Quattro, with the ZF5HP19a. It went into limp mode at 138,000. Stuck in third, and the PRNDS in red.

I was prepared to condemn the tranny, but decided to try an oil and filter change, as described in AudiPages. It cured it, I sold the car with 160,000 on the odometer, and it never missed a beat, I also drove through France to Spain, and it didn't let me down.

So yes, it's possible an oil and filter change may do the trick. Sure you've had this done, but there are no guarantees it was done properly. Or the oil grade and level are correct.

I wish you all the best.