Derek 6193

this is a complicated issue, please bear with me. its about the transmission, and/or TCM, but all of this matters.

my car, a 1996 Audi A4 2.8 Quattro (automatic) began having transmission issues a couple of weeks ago. Here are the symptoms:

I just replaced the engine. the engine was replaced by a good mechanic I know, who is not an Audi specialist, but just a good all around mechanic.

after the engine was replaced, it started doing this:
-tachometer not working and every light on the dashboard was on, oil light, fuel light, engine light, absolutely every light.

-then it would switch, and the tachometer would begin working, and the lights would go off.

-then it would switch again, and the tachometer would quit working again, and all of the lights would come back on. I assumed that was an issue with the transmission input sensor.

I drove the car about 300 km, and then the transmission started acting like there was no fluid in it.

I took it to an Audi specialist, who topped it up and told me other mechanic had not put any in after he replaced the engine. ( I called the first guy and he said he didn't take any out)

I drove the car bout 20 km and discovered a transmission fluid leak at the radiator.

I fixed the leak myself, apparently the hose wasn't tight enough. then I assumed it would be low in fluid again, so i went to check it and tons of fluid poured out. After it was finished pouring out I checked the level and was fine. the Audi specialist had both not spotted the leak, and had also over filled the transmission, about 3 litres too much.

then the car started doing this

the lights and tachometer issue continued, and at the same time, the transmission had difficulty going in to any gear. ie: if I was sitting at a stop sign, when I tried to go, the engine would rev and the car would not move, but then would suddenly lurch forward. I read the codes and it was telling me there was a transmission ground fault.

it did this for a few days, and then the transmission stopped working altogether. the engine would rev, but I could not put the car into any gear, it was like every gear was neutral.

I had the car towed (because I live int Toronto, and the mechanic who replaced the engine is almost 200 km away, and because the Audi specialist had put in too my fluid, I decided not to use either of them, and went to my friends mechanic, who is a BMW specialist.

I sourced a used transmission that is apparently from a 2000 Audi S4, but I researched it and supposedly it is the same transmission. I was also told that it was Plug-and-Play and that no programming would be required) I bought it, and the BMW specialist installed it for me, took the car for a test drive and immediately the car went into limp mode.

he read the codes and it was still saying the same thing. also apparently the issue with the lights on the dash remained the same.

the new transmission came with a new TCM, so he tried replacing the TCM with the one from the S4, but after it was installed he could not communicate with it.

he put the old one back in and and the same code and light issues recurred again.

he also says the OEM TCM looks like it has gotten wet, the contacts are corroded on it. He thinks this is the reason the transmission burned out.

at this point he washed his hands of it, and does not want to go any further with it.

I went on to an Audi forum on facebook and asked for recommendations for Audi specialists, and called 2 of them.

The first one said, "duh, I don't know".

The second one told me that the TCM needs to be reprogrammed for my car. but it can only be done by Audi themselves because they wont give the codes to anyone.

I walked in to an Audi dealership in Toronto and asked them about it.

they say that the S4 transmission, thought it is "the same" is not actually compatible, and the TCM for it, will not communicate with my ECM. this is why he could not communicate with it.

they also say the A4 TCM will not work with the S4 transmission, and this is why it went into limp mode. they say I have to put an OEM transmission in it.

(my dad says that the guys at the Audi dealership are only taught certain things, and are not capable of thinking outside the box, he is also in his 70's and is accustomed to cars that dont Have computers on them) Anyway...

I asked the Audi mechanic what would happen if I put in an ECM from an S4, they said it may work, but it would take a while for it to "re-learn" everything, and "might" never be efficient.

what does the hive mind think?
-should I put in the OEM transmission? or
-should I get a new A4 TCM? or
-should I try using the S4 TCM and getting an S4 ECM? or
-any other ideas I have not thought of?

Thanks.

the_duke

An S4 ecm isn't an option. Someone more knowledgeable will chime in but I don't think you can use an S4 TCM with your A4 ecm. You might also run into issues with the transmission. I'm not sure if the gear ratio is same between your A4 rear end and the S4 transmissions from dif.

Derek 6193

ECM? ECU? I'm getting my terms mixed up. i am referring to the main computer in the car.

the_duke

Edited my post.

clancy

Your Father may be correct. Nevertheless, mixing and matching different years and different platforms (A4/S4) is not nearly as easy or successful as you may have been led to believe. I would look for an Audi indy who specializes in speed work or just really knows the computer end of Audis. A shop that is adept at routine maintenance of Audis is not necessarily one who will understand the idiosyncrasies of making an Audi hybrid. And, many do not wish to get involved with one that has mixed parts of different platforms. This can quickly become too costly to sort out at the going labor rate. Especially on a 1996 that may never again be worth much.

There is an Audi website for people who tweak the computers as a hobby. These people know how to mix and match better than most. Don't remember the name, but you can likely Google it.

Finally, Audi transmissions have a specific way of checking fluid level. Needs to be done while the engine is on. If checked when shut off the fluid will run out. Are you sure this was done correctly? This procedure is easy to find if you search this forum.

haliboo

Bumpers

4Driver4

"I fixed the leak myself, apparently the hose wasn't tight enough. then I assumed it would be low in fluid again, so i went to check it and tons of fluid poured out. After it was finished pouring out I checked the level and was fine. the Audi specialist had both not spotted the leak, and had also over filled the transmission, about 3 litres too much."

This sounds like you checked the level without the engine running. If so, the first trans was low on fluid, which is what killed it (assuming it actually was dead when removed). It's almost impossible to overfill one of these transmissions but more than half a liter or so.

At this point, I'd probably move on. This car is parts. Not trying to be nasty, it just seems like you've got a bunch of issues on an older car that has very little value, when you could find something else for reasonable money.