Danny Guo

I can't believe this! My 1996 A6 2.3 has been making buzzing noises when the auto transmission shifts from 2nd to 3rd.
The workshop says a defective radiator caused coolant to enter gearbox. Hence I must change radiator, coolant unit AND gearbox!! Gosh is this possible? and isn't this a design flaw? Do other continental cars have this kind of design? Am I being taken for a ride???
Thanks Danny

muhammadc

I'm no mechanic, but I don't see how that is in any way possible. The transmission is a sealed unit... Maybe a second opinion would be a good idea at this point.

JKR

Like Muhammad said, the gearbox is a sealed unit and this sounds like a quite precarious scenario. get a second opinion.

Jim Selders

Do you have a separate xmission cooler? It could leak into the gearbox.

DWC_2.7T

I'm not familiar with your model, but I've never seen a water-cooled transmission. Trans coolers are usually direct heat exchangers, typically located below or next to the radiator. Theres no path for engine coolant to reach the trans. Either your diagnosis is fishy or Audi used a truly wierd design.

Augie

Many, many manufacturers use a section of the primary radiator as a heat exchanger for the transmission. I don't know if Audi does on this model, but it's pretty easy to find out. All you need to do is check out the radiator, and look for a pair of quarter-inch tubes (typically on one side or the other, near the bottom), much like brake lines or a little larger, that lead to and from the transmission.

This wouldn't prove that the tranny guy is correct, but it *would* prove that it's possible.

Deutschdan

Well, it is possible to get water into a transmission on "some" cars. When I was a teenager, I did my dad a favor by flushing the radiator. During the radiator flush, some of the water splashing around the enginge compartment entered the transmission, through a breathing tube I'm guessing.

Weird, but true.

Bollinger

Many manufacturers use a heat exchanger (water to water radiator) inside the main radiator to cool the tranny fluid. This may seem dumb, how can you cool fluid by passing it through a radiator full of 160F fluid?

Well, it acutually works very well. Yes, you cannot possible cool the fluid down past 160, but the advantage is that you have water (liquid) on both sides, and water is a much better conductor of heat than air. So, the radiator water takes heat away much faster. You can't cool the tranny fluid down below 160F, but you cool it with a much smaller radiator than you could using a water-air radiator.

ChrisS -2008 A6-4.2

92 100CS 130K miles radiator and trans. cooler mind-melded and coolant entered the auto-trans.

Had to trade the car as the repair was only $2K less that the trade they offered me.

Seattle Scott

After looking for information it appears :

1. As other people stated a section of the radiator can be used for transmission fluid cooling.

2. I didn't find any people saying their transmissions were permanantly damaged after having the radiator fail and the fluids mix. They got fluid changes and new radiators and all seemed well.

3. Afer mulling it over I like the design idea. My initial reaction was "What a stupid design" but I like the idea of probably having a more consistent transmission fluid temperature for a reasonable cost. Considering the usual consequences of a failure (appears to be a fluid change) versus the possible advantage (more predictable tranmission behavior) I like the idea.

4. I may be totally full of BS too or thinking about this from the wrong "angles".

You might want to look at your antifreeze and see if it looks normal or has oil in it or is "milky" looking. May the coolant smells oily.

If your car is like mine (97 A6 2.8) you probably have Audi/Volkswagon "Red" antifreeze (look under the hood on the driver side for a sticker).

Do you have a dipstick for the transmission you can pull and have a look at the tranny fluid?