Not happy
 

Have just been informed that due to a undetectable failure in the radiator or the transmission cooling tank, that transmission fluid has now filled the radiator and coolant has filled the transmission. The dealership is $5300.00 to replace the transmission and flush the radiator.
How is this even possible?
How do those fluids transfer, shouldn't they be totally separated?
Is there a recall I should know about?
I'm pissed and ready to go to war with GM.

1) Please list, very specifically, what you are driving (08 Vue XR 3.6 V6 for example)

2) Yes, those fluids are cooled in separate "chambers" inside the radiator.
I'm guessing the metal dividing those two corroded, allowing mixing of the fluids.

How would they corrode?

08 saturn vue xe awd? ???

The trans cooler inside the radiator will corrode if the engine coolant is not flushed and replaced with new fresh coolant about every 50,000 miles, regardless of what the maintenance schedule calls for. Coolant does break down over time, not only loosing it's ability to cool and lubricate, but also to provide corrosion resistance.
It is also possible some other repair has been done in the past, like a water pump replacement, where the proper mixture was not observed, or the wrong type of coolant was mixed-in.
There may have also been a overheating problem at some point, where the severe temp differential between the coolant/eng temp, and the trans fluid temp may have damaged or cracked the internal trans cooler. This is not usually a common problem, but it does happen, especially when Dexcool degrades, or has been mixed with something else.
At my shop, we recommend flushing the cooling system every 50,000 miles. We also don't flush with Dexcool, because people usually leave it in too long, and will cause a host of other problems from head to intake gaskets. We use universal yellow Peak, mixed 50/50 with distilled water, not tap water. Tap water is too hard and can cause deposits and blockages to occur in the radiator inner tubing.

well, I guess I know what my next two maintenance tasks are.....

the OEM anti-freeze around 07' was having problems with eating things like the head gasket and such in the cooling system. A bulletin was released saying to flush it and refill with a new OEM replacement. Most likely this could be your culprit.

I flushed my system repeatedly to get all the (bad) anti-freeze out.

So I've gotten the same feedback from multiple people now about the trans cooler and a failure with a metal dividing wall. My question now......mostly to GM is ......If you are aware of the possibility of these fluids breaking down and possibly corroding the metal they are housed in ........then why build it that way?
I am not a car person. ...The vehicle gave no warnings no engine lights nothing to let me know this was happening. Now I've a car that doesn't work and possibly a $5k bill to fix a vehicle that is only worth $8k.
I am calling out GM on this one.....man up ...admit you're at fault and fix the issue.
My next step ......posting this story everywhere online so people can know how ****TY GM is.

not possible to have warning lights of this nature. I complained to GM bout the control rod ends I had to replace on my Saturn, but it fell on deaf ears. BTW, I have heard that there is a Cavalier (94'?) control rod end that will fit the Ion and is vulcanized construction for durability.

I turned to Saturn when the GM work horses started to fail and leave me on the side of the road. Seems the cost cutting burned me with Saturn as well, but have not left me on the side of the road.

Chawala.....well I am dead on the side of the road :(