silverd2

I did mine at about 100K miles, mostly out of curiosity (under $200 with all the right stuff...brand of filter makes little difference, so long as it fits and the pickup is not too long) ...just wanted to look in there...and had a little of the occasional hard downshift to 1st gear (1 out 10 downshifts, maybe).

If I had it do over, I would have pumped the old ATF back in and gone with the new filter only (always a good idea), but had 8 liters of new stuff on hand already...old ATF still had good color, smell and no shavings on the magnets...BUT the filter was apparently a bit constricted, since the hard downshift went away mostly (only once in a blue moon now).

IMHO, if you find burnt fluid and lotsa shavings on the magnets, yes your trans is probably shot anyway and on borrowed time. I believe, by simple logic, new ATF at that time will simply speed up the transmission's eventual demise. For much the same reason that a simple drain and refill (without changing the filter) is a stupid move...new detergents in the new ATF will clean up more deposits and send straight to an already partially restricted old filter...bad move. By the same logic, new ATF detergents can clean off beneficial deposits acting as friction aids on otherwise worn (near failure?) clutches in the trans. This makes sense to me and many others who have reported total failure shortly after service on trans's with burnt fluid and lotsa shavings....coincidence? ...I'm prone not to think so...failures of anything shortly after service point me to believe "bad idea" or incorrectly performed service.

Cheers

nossisnave

This made me think of something, I'm not sure how often it occurs. I heard of it when reading about doing the procedure on an RS6. The problem is with the filters: due to differences between the A8 and RS6 transmissions, there are a few different sizes to the pickup tubes that sit down in the bottom of the pan and draw in fluid. If the wrong filter for the transmission was ordered you could have one with the longer tube being matched to transmission pan that was too shallow and shortly after replacing you'd have catastrophic failure I can't remember who was in the habit of measuring the depth of the pickup tube and cutting it if too long. I wonder how many times that has been the reason for a demise of a 5HP24. This would certainly be "incorrectly performed service".

nossisnave

And now that I read more carefully I see Silver already mentioned that. Whoops. Sorry for the duplicate post.

ejmeier

Well, I took it to a different shop today and had the filter and fluid changed (for much less than the $700 mentioned by the other shop). He said there wasn't any metal shavings in the pan, but the fluid smelled burnt.

On the drive home, the symptoms persisted, and maybe got a little bit worse. I guess all that's left at this point is to drive it till it dies...