Audi C4 2.5 TDI - Transmission oil in coolant

Hello, I'm a new member and already have a question: I bought an engine (AAT) with approximately 230,000 km on it, used. The seller mentioned that the car had a transmission problem. At home, I discovered that there is transmission fluid in the coolant, and I'm wondering how that got there. The engine oil looked good when I drained it.
Is that even possible, and if so, how? Has anyone here ever heard of or experienced something like that before?
I would be grateful if you could help me.
Regards, Stubi.

Hi there,
I completely agree about the "gear oil" issue; how would you even know what kind of oil is in the water?
However, I claim that the AAT, when used as a 5-ender, only has one ZKD (presumably referring to a specific technical term).
Happy New Year!

Olli.

Hi,
Fortunately, the AAT only has 5 cylinders .
However, I would still immediately change and flush the oil. If there's oil in it again later, then proceed as Rainer suggested.
Can motor oil change the smell of the coolant?

Someone was faster.

Hello, thank you for the responses so far, but they aren't really helping me much. Yes, it's a 5-cylinder engine, and I forgot to mention that it's an automatic transmission. Apparently, this particular model is supposed to have a heat exchanger between the internal engine cooling system (water) and the automatic transmission fluid (ATF). This heat exchanger is supposedly defective. Unfortunately, I don't have any technical documentation myself to assess the situation.
Best regards, Stubi.

Oh yeah. If the automatic transmission of the four-cylinder engine has that feature, then the AAT probably does too.

It's probably similar to the V8, where the transmission oil cooler is integrated into the water cooler. You can tell by the two steel lines that are connected to the water cooler with hoses.

Buy a new radiator and change the transmission fluid, including the filter inside the transmission. You might also want to flush the transmission with oil once, then refill it completely.

Regards,

Cord.

'If the oil looks almost like black threads, it's definitely transmission fluid. It also cost me a new radiator, at roughly the same mileage. Fellow sufferer... it really adds up.'