1998 Silverado - white smoke from engine NOT tailpipe

350 5.7L. Automatic 4WD. 140,000 miles
Not losing coolant, not overheating. Starts easy, runs fine, shifts fine.

I can see white smoke. Open hood. The smoke is coming from the passenger
side of the engine, below the A/C accumulator (that big silver can
on the firewall on the passenger side). (smoke is NOT in the exhaust)

It sure looks like something is dripping onto the hot engine or exhaust underneath, making the smoke.

Whatever it is, it is NOT coolant. It doesn't have the right smell for that.
I've had that happen, and it always has a sickly sweet antifreeze smell.
This ain't like that. It's oily - I'm guessing either engine oil or transmission
fluid.

It just did it for the first time this morning after about a 1/2 hour drive to work. There has been no hint of this at all until now (i.e. I have not been using any oil or transmission fluid). Drove it again at lunch, did it again as soon as the exhaust/engine heated up.

The other remote thing is that rubber shroud around the A/C accumulator.
That's been deteriorating, melting away, and turning kind of "gooey" for months, and I'm wondering if a chunk of that
rubber lodged itself under the truck on the exhaust - although I cannot see anything.

Okay, an update. It is definitely leaking transmission oil from the front of the tranny somewhere. It's kind of hard to tell because it drips and runs all over the place, but it is NOT from the rear of the transmission, the pan, or the transfer case. I'm guessing a front seal? Or maybe where the cooling lines
connect?

Fluids will run down and back from the leak so look up and forward. Note color and smell of the fluid.

Turns out it was a corroded cooling line, so it wasn't so bad.
$90 to replace the whole line from the trans to the radiator.
(I figure 1 - 1.5 hrs labor, seems reasonable)