Hi folks,

Let me be brief and if you have more questions let me know.
I have a black sludge in my overflow bottle. My radiator fluid is blackish, NOT brown, but black. I have a leak in what I think is the transmission, a small reddish, brownish dime size puddle under truck.
My motor oil is super clean on the dipstick and NOT showing low on oil.
There is NO smoke coming from the tailpipe.

What is this blackish tar colored fluid I'm now getting?

If you want photos, do let me know.

 

Wait... what? Transmission? Radiator? Engine oil?

I can see engine oil and coolant getting mixed......... but what does the transmission have to do with it? They aren't even close to being able to mix.

Unless you put the wrong fluid in somewhere.

 

I was told by my mechanic that on an automatic, there is a "transmission fluid cooler" on the side of the radiator, and if that cracks, transmission fluid and radiator fluid can mix.