2008 S8 Trouble with the transmission
 

Every now and then when taking off from a dead stop the car will hesitate like it is in neutral and then slam into gear. And I mean SLAM!!
I had the local Audi dealership check out the transmission and they said they ran it through the program and can find no problem with the way it shifts.
Anybody ever run into a situation like this?

2208 S8 Trouble with the transmission
 

Wondering if it is because your transmission is from 200 years into the future? Sorry could not help myself there, sorry I have had no similar experience with my transmission. Some minor lag from full stop only on occasion, but never slamming, hopefully others can advise.

Oops!!! :)
Changed it to 2008.

Warp coil transducer? Time rotor ?
Attachment 103906

Sorry, couldn't help myself either.


Any codes or scan ?
Wondering if it is fuel and/or vacuum related.

Would a can of Trans Medic be appropriate here?

Don't know if it can fix a bad turbo encabulator. (Youtube this term). I worked for Rockwell International during this era.

Does it happen in Drive or Sports mode?

Mines done it twice but only in sports mode, when rolling slowly and it like it suddenly drops from second to first when I started to accelerate.

Step 1: check fluid level. Step 2: pray it's just solenoids if step 1 isn't it.
 

First check fluid level per the std. procedure--car level, running, open fill plug below 40C, etc.--it's on the web or ZF's site if you or mechanic doesn't know it. Also in Bentley repair manual. Many shift issues are caused by wrong fluid level/leaks, etc. Obviously if it is wrong (low), fix the leak.

Next, if it is not a fluid level issue, pray it might just be only a bad solenoid and not worse.There are a bunch of them in the transmission valve body, now called "Mechatronics." As I understand it, they are no longer just on/off flow/no flow but are variable in their control ability. In turn that makes them vulnerable to wear and leakage and such, plus outright failure too. One of them deals with the 1-2 shift specifically, though others can be implicated too--two in concert determine the specific gear, plus there is the torque converter lock up--which on the 6HP26 can be in many of the gears, not just the top one like in the "old days."

You either need specialist knowledge or a good ZF tranny shop to get into this. ZF sells the solenoids individually or in a kit, plus offers rebuilt valve bodies. A set of ZF solenoids is in the $500 range from ZF suppliers, and the rebuilt valve body well over $1500. Fluids, gaskets, seals, etc. will cost the better part of another $500; none of it is a sure fire fix either if it turns out you have other issues w/ clutches, bushing wear or otherwise.

Dealers under warranty typically only replace the whole tranny, though they sell a valve body as a separate part (for more than ZF does). Valve bodies also have to be coded to the vehicle if you don't use/rebuild the current one.

If you end up at part 2, search ZF and 6HP26 on the web, maybe with terms like "shift issue," clunk, thud, etc. If you dig around a while, you will find a bunch of posts from the BMW world since the same tranny in RWD flavor was used w/ lots of larger BMW's. They will typically back into the same items above, and have reported success when they have done solenoid replacements. I've seen very little good diagnostic information on the 6HP26 in the Audi applications; there is a bit around from Jaguar, plus the BMW forum info I've come upon in the past.

Solid advice. I know some guys have had issues that were solved with a Mechatronics replacement. It's not ALL that difficult if you're used to working on these cars (beyond just routine maintenance), but yes, despite having the car out of commission for a while, you do want to have your unit rebuilt, not swapped for another, as then you open up all sorts of coding issues.

How many miles do you have on the car? If higher mileage (say over 75k), it might be wise to try a fluid swap to fresh fluid (which will also get your level correct in the process) to see if that doesn't get things operating better. If this isn't the solution, then you're on to step 2 which is likely a Mechatronics rebuild.

The car has about 73,000 miles on it.
The issue with the transmission only happens when taking off from a dead stop. As I initially accelerate it seems like it goes into neutral, the engine rev's and then it slams into gear.
It also only happens after I have been driving for a while. It doesn't seem to happen when the engine/transmission is "cold".

Net, same advice as already posted.