Down shifting When I come to a rolling stop, the transmission does not seem to get to a lower gear such as first. Sometimes this continues when I have come to a complete stop. Sometimes when slowing through an intersection I may not have the power I once had as it is not in the proper (lower) gear. Then when I hit the gas it jumps into the proper gear. Makes me nervous and less confident than I have been before. Car has 128 kilometers on it. Have changed the tranny fluid recently. Problem getting worse, I think...

I went through this on a 96 A4, tried the transmission fluid change (no luck), cleaned every electrical connector under the car with ProGold electrical contact cleaner (didn't fix it), and finally narrowed down the diagnosis to a failing transmission control unit (TCU). Another guy with an identical car offered to let us use his TCU for diagnostic purposes. We swapped it in and the previously-stricken car ran like a champ.

The TCU in the A4 was located beneath the carpet in the front passenger footwell, just in front of the seat. The kickpanel and sill plate were removed, the carpet pulled back, and a black box is exposed. This is the container for the TCU, and it has a large bundled cable going into it from the kickpanel area. Open the box, disconnect the cable, and remove the TCU. Install the new one in reverse order, put the car back together, and try it out. In our case, it worked great.

Before shelling out for it though, you may want to do a scan of the car using VagCom (the Audi diagnostic software). You can download it for free from www.ross-tech.com, and the interface cable to connect the car to your laptop is on eBay for around $20 (do a search for "audi a6 diagnostic cable" or something to that effect and it'll show up). You'll get a limited version for free, which is still pretty powerful, but paying $100 will buy you the full unlocked version used by professional shops. This version has none of the functional limitations of the base free version, and will allow you to do full chassis/body/drivetrain/climate control scans, as well as ECU scans. You can check and clear codes with it, adjust idle speed (and I believe timing as well), and recode the car for many useful locked features (such as the ability to open/close the windows using your remote). For anyone with an Audi, it's a great investment - one time purchase is the same as paying a dealer once to scan your car - this way you can do it yourself and save a ton of money in the future diagnosing your own problems.

The TCU is expensive to buy new (I've heard quotes of $1600), but can be purchased used with a guarantee from Shokan Salvage (www.shokan.com) for around $240. If you're reluctant to buy the VagCom software, you could go to a Euro-specializing shop and have them scan for codes to see if they can confirm the TCU one way or the other, and then go from there.

Hi,

Basically, in my view the kickdown has to be adjusted so that it would shift down earlier as it is currently set at. This is a relatively easy work done but preferable performed by an authorized or knowledgeable Audi mechanic.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards. Thank you for using FixYa.

Check Transmission fluid is very important to an automatic transmission. All of the magic happens in the fluid. Most cars come with red transmission fluid, good to know if you are looking for a leak.