everwake

I have an A8 with about 100.000 miles on the odo.

I have had issues with harsh downshifts from 4th to 3rd for some times.

6 months ago I changed filter and oil, after adaption the transmission was behaving better, but it did not last.

today the downshift are quite hard and I probably need to get this fixed.

I have read alot about 6hp19/26 and downshifting between 2nd and 1st, but that is not my issue.

any ideas on what the probable cause coould be?, solenoid? gasket? entire mechatronic, torque converter? google has failed to shine light on the issue.

I have an appointment scheduled with a ZF expert, the problem is he is the only one in the area and he knows it, he quoted med $1100 just for the solenoids, so I want to be in the know before I go there.

Jack88

Hard 4-3 is unusual. I think you can replace the solenoids individually, if you can find a diagram telling you which is which, so you can replace just the faulty one. $60 each or so, IIRC. I think it sounds like a logical solution to your problem, but it still could be something else. $1100 is a lot to throw at what sounds like a guess.

Shamoye Lewis

for $1100 change the whole tranny.... D3 tranny dont usually give issues.... should try to also can it and check the measuring blocks... before you dump all that cash

dvs_dave

What ATF did you use for the refill?

MP4.2+6.0

+1 on this as a preliminary. And, is it at full level when warm, level and running--as in, correct fill procedure followed?

After that kind of a guess on where to go. If it's a clutch or bushing wear, then it's done. No way to really know that absent teardown.

But, more likely fixes are new solenoid set and/or just the seal from Mechatronics valve body to the transmission case. A fair guess given my own experience is is just the latter seal. But to get at it, Mechatronics has to come out along with fluid and filter change, so you get into whether maximizing chance of success by doing both makes sense. Solenoid set is $4-500, or at least what I paid for it. Plus labor. OR, have them drop Mechatronics. Then look for seal distortion. If found, replace and wrap up. If not, proceed to solenoids. Seal issue is (somewhat) known on 6 speed ZFs, more so in BMW applications. To be clear, all of this work can be done once pan is off; no tranny removal is needed.

See my replies here: https://www.audiworld.com/forums/a8-...ssion-2866629/. And the earlier post, reply 9 here: https://www.audiworld.com/forums/a8-...stems-2868586/ Lots of info and background there.

BTW, if he means $1100 out the door for the solenoid job, likely not bad. But, be clear what that is. Should be solenoid set, Mechatronics seal, new fluid, filter and gasket. When you add up the parts and ZF fluid at price you would pay for, he only has a few hundred in labor in there. That's quite reasonable given pan drop and then Mechatronics drop work. Took me several hours on Mechatronics drop and install (especially the linkage), and a few more hours to (SUPER CAREFULLY) disassemble to change solenoids. It's a lot of heat soaked plastics and wiring connectors, and the TCU is actually in there too. Note again if he finds bad seal, you could just stop there. But, also a question of what parts to order in advance, out of service time, his lift, etc. Mine did go from 100K mile "used" feeling to virtually brand new shift quality wise, so not lamenting I did both.

everwake

$1100 was for just the solenoids, no gaskets, oil or work...

yesterday I ran a scan - came up clean, test drive, no detectable slipping even on repeated accelerations through all gears, even though I pushed hard oil temp never got above 72 degrees celsius, so faulty torque converter seems out of the question.

reset the apation on the gear box, and after learning new behaviour nothing has changed, still smooth through all gears expect 4-3 downshift, if the gasket was distorded I guess I should be having som issues in other shifts as well?

the oil used was ZF 8 oil, job one by a very reputable shop, they service a lot of tuned and racing audis, they seem to know what they are doing.

my car is a 3.0TDI, so separate oil systems, read both those threads and many more, I guess I just have to decide if the thud on downshift is a problem or not, oil change was 10 months ago ( not 6 like I wrote) and the oil was in very good condition.

Shamoye Lewis

put car in tiptronic mode and manually change the gears at about 4000 - 5000 rpm when you hit 6th gear down shift manually so how it feels down shifting

MP4.2+6.0

FWIW, when my issue came up it was 6-5 downshift only, not any other. Yet per pics you can see the obvious distortion in the seal I took out. If I remember right, the BMW types most often pinned it to 2-1. So, it seems to vary. Or, it was a solenoid after all. Whatever it was, it was gone completely post work I did.

Since you have a TDI, you might be in a more expensive parts market than USA. I got mine from what used to be one of ZF's master distributors and the old lead for Audi based transmissions. They seem to have reorganized though to where they have lots of distributors and they cover all car makes. Mine is a W12, so obviously low volume. Didn't seem to matter though for parts cost.

As I said, if shop is cooperative, you could try just pulling valve body and assess condition of seal first. You could check in advance what the solenoid set lead time is. If you did not do the 3 times fluid change, you probably should over time anyway, more so in shifting from ZF6 to ZF8. Any one fluid and filter change only gets about ⅔ of it changed, and I found obvious color shift to new fluid only really showed up after 2 changes. FWIW, I tried the same stuff you did--fluid changes, adaptation, etc. Also got the "honk" reflash. None of it was the solution until the internal work.

jlbell

I wouldn't say I have the similar concerns as the OP but I have a few upshifts from 2 to 3 that may be a bit noticeable to say the most. However when shifting manually with tiptronic it goes away. I have narrowed it down to the adaptions, which I have lost the ability to reset after the most recent VCDS update. Ross-Tech claims that I have never been able to clear the adaptions, but I know for a fact at the beginning of the year I was able to before their most recent update. My A8 is a 2004. If anyone with an 04-05 can clear adaptions with VCDS please let me know how. I was having the same concern at the beginning of the year once clearing the adaptions the noticeable shifts went away. I have also read of a TSB that stated their is an update for our transmission modules as they do not know how to adapt to wearing friction material (clutches). I have yet to find it but I know it is out there and different from that one of updating to ZF lifeguard 8 whenever the TSB stated if you updated to Lifeguard 8 you needed to updated the module for the updated viscosity values of lifeguard 8. Sorry for my rant but Ross-Tech has been upsetting me for the past few weeks where they are blaming me instead of looking into their software before the most recent revision.

everwake

for me changing manually does not matter, still harsh

mine is year model 08, and I use an ancient vcds version version 12 or 13 something that I have on an old laptop, clearing adaption worked for me.

I will probably go by the expert that ZF recommended in a few weeks so he can test drive, I will make sure to update the thread when I have been there.

In Sweden where I live, spare parts are expensive, and labour ever more so, my plumber that fixes my pipes at home charges as much per hour as I do being an IT-architect with 20 years of experience...and to top that off there are very few alternatives when it comes to ZF gearbox savvy techies...and looking at probably around $2000 to fix an annoying thud doesn't really appeal to me, but we will see what the diagnosis is.