gubro30 has it correct.... 2 seperate problems

Thick white stuff in the water is called Mayonaise and is the result of oil and water being mixed. -This is a big problem! Do you see the same thing when you pull the dip stick? If yes don't drive the car because your using water to lubricate the bearing - a very bad thing - If no you need to find out how the oil is getting into the water - 90% chance it is the head gasket -

Transmission oil / seals is a seperate problem and could easily cause the slippage your describing.



I can't tell you how much it will cost - but find a good indy and bring money - lots of money!

Maybe some can stear you to a good indy in your area.

 

Cars with automatic transmissions usually have a transmission cooler in the radiator, which may fail. When this happens, ATF will leak in to the coolant and coolant will leak in to the ATF. Since Audi doesn't have a transmission dip stick, this may go unnoticed and lead to transmissionfailure.

 

i bought a CPO 2005 A6 and it seems to have the same symptoms..
Do you think this would be covered under the CPO warranty?

Also, we were driving on the road (10+ hours) and towards the end, the car just shut down twice as if it was out of gas....
Any ideas?