nadinep

Hello,

We own an Audi A8L Quattro and it has a issue that is stumping our local dealer to the point of wanting to throw expensive parts at it in an effort to fix the problem. When you put the car in drive in the morning most of the time (not all of the time) the transmission does not work correctly. If you turn the car off and restart it, it will drive correctly. In some occasions we would have to restart the car a few times in order to get it driving correctly. We decided to take it to a dealer to have it troubleshot to find out what the issue is. My little cheap code reader said "Transmission solenoid D Electric". The dealer tried to trouble shoot it for a diagnostic fee. They told me the code was not definitive and they had to pull the pan to check the solenoids in the transmission(and the price went up). When they pulled the pan they found that all three solenoids were not operating correctly and thought it strange that all three solenoids would fail at the same time. This turned them in the direction of wiring or control problem. They found the battery was down to ten volts in the morning and thought it was possible that the low voltage could be the problem. They charged the battery and the problem persisted. Next they tried testing circuits by hooking each circuit up to a tester for 8 hours at a time and noticed something randomly turning on at night or whenever it felt like it draining the battery below 12 volts. They could not identify what was coming on so we just changed the battery and that seems to have stopped the random discharge(the price went up again).

The car has been at the dealer for about a month and they want to change one of the solenoids to see if that is the problem ($700.00). If that isn't it they say it may be the computer. Next step, change the computer ($1800.00). Apparently what is happening is when the car starts a transmission fault is kicking the car into limp mode. When the car is restarted, once or twice, on bad days three times it starts without a fault and drives fine the rest of the day. I'm going to be into this thing 2k for a new battery. I know the dealer has put lots of time trying to figure this out and has not been nailing me as bad as they could but I am reluctant to start throwing hail Mary high dollar parts at it. Anyone have any ideas, anyone to talk to, contacts?

Thank You

MP4.2+6.0

my first instinct would be just to do a tranny fluid drain and replace, including the filter. Just using the stock gold fluid for 4.2's, and not the pricier "blue" from the W12's sometimes used with 4.2's to cure a noise issue.

The solenoid change will invariably result in a fluid and probably filter change, but I would tend to just the simpler first, especially if the solenoid diagnosis isn't very definitive.

Another alternative is to have the tranny work done at an independent who can pull the valve body (where all the solenoids are) and get it rebuilt. I did that on my 2000 Audi C5 A6 4.2 with the predecessor 5 speed AT and a solenoid driven valve body. The rebuild cost on the valve body was about $500 some years ago, with me doing all the other labor to remove and install, plus fluid and filter change at the same time. Shifting was like new afterward [I had bought it new, so new how it drove from early on]. Took about ten days of total down time with me shipping it from CA to a ZF specialist rebuilder in CT.

mishar

I would also check that battery. How old is it?

snapdragon

" on so we just changed the battery and that seems to have stopped the random discharge(the price went up again). "

pmdeaver

I had something similar happen ONCE about a month ago. I was driving to work, went to pass someone, and the car wouldn't down-shift for the pass and kind of got stuck in the gear it was in. I slowed down, drove to the end of the road, turned around and went back home. There was something visibly wrong with the transmission and an odd noise coming from under the hood.

When I got home, I isolated where the noise was coming from and actually took a picture of the part in order to post here later. I powered down the car and went inside to sulk a few minutes.

When I came back out, I cranked the car, the noise was gone, and I've never had another issue with it. I'm assuming maybe it was just a software glitch that worked itself out after "rebooting" the engine.

nadinep

No one is sure it is the valve body MP4. Everything looks and seems to be working correctly. Something is throwing a fault. I guess I'm going to let them roll the $690.00 dice at my expense and hope its the problem. Going to replace the module that the fault code points to most of the time even though it looks to be okay.

MP4.2+6.0

The solenoid you refer to is...simply part of the valve body, unless you are using the term solenoids twice in the post (the 3 solenoids the dealer said weren't working correctly, and then the one for $690/$700) but for some completely different part of the car. On the six speed the whole subassembly is called "Mechatronic" in ZF speak, but it's generically the valve body.

From having been through this pricing back on the A6 C5 4.2, the Audi pricing is many x the piece pricing from ZF, which is where the parts come from to begin with. I suspect you can get the whole valve body all checked, rebuilt and all at a parts price similar to what you are talking about for a single solenoid. From my A6 experience, I remember kind of guessing at which of several solenoids it might be, and adding up the price to a big $ number. That's when I checked the ZF rebuilder system out. These guys (Eriksson Industries in CT) rebuilt my whole A6 4.2 valve body for something like $500 six or eight years ago; worked like new afterward: http://www.zftranspart.com/index.php...&parent=1&pg=1 The link talks about Bimmer 6HP-26's, but at least when I used them in ZF's prior smaller distributor network, the west coast place (where I live) told me Erikkson was really the ZF lead on Audis, at least at that time.

ltooz_a6_a8_q7

The Audi ignition seems to control many things electrically. When the ignition is old and loose (due to tons of keys on the chain), the return spring action and contacts are not 100%, INTERMITTENTLY fails that's why when you restarted the car many times and it hit the right one and it worked.
Now, A8L has smart starts (keyless), does it work with smart key?

About the solenoids, if they're $700 a piece, ask the dealer to take it out before replacing it, put it on a bench with variable power supplies (0-24V), test it, either it clicks or it doesn't when the voltage is applied to it, measure the resistance between terminals. "they don't work properly" what does that mean for SOLENOIDs? What are solenoids? especially in AUDI transmission? It does look like a witch hunt to me.

Cheers,

Louis

nadinep

Well, we rolled the dice and it seems to be working correctly so far. After a few weeks I will be certain it is fixed. The service guy referred to it as a module. To make a long story short we got a new battery and module for 2k. Could have purchased a used Toyota Corolla for that! We have our fingers crossed, so far so good. Thanks for the replies.