Okay today (to save money) I tried spraying air from an air compressor through it. The flow came out just fine on the other end, and the fluid that came out was the same condition as everything else, no chunky nasty stuff.

So I went ahead and removed the cooler. Added 4 pics to the album: https://photos.app.goo.gl/e35yspoB9sM2FYy2A

What I noticed is that one half of the cooler looks burnt, while the other half looks just fine! What exactly is going on here?

 

Ok, that's odd..... I am guess that is the side facing forward... so, probably what you are seeing there is just dirt and such it collects from the road. Hopefully, no big deal. Try rubbing some off, see what ya get.

You have a compressor? That's good. Pour some mineral spirits in there, then force it thru with air. Do that several times, in both directions, until it comes out clean.

 

Should the cooler lines be plugged into the radiator at all, or just straight through the cooler? On mine the cooler lines are not connected to the radiator at all, but on most diagrams online its supposed to be that way.

 

If you aren't using the cooler in the radiator, then don't worry about it. But, if you ever DO decide to hook it up, clean it first.

 

Well that's the thing, this is how the truck has been since I got it. I'm just now looking at these things and realizing them.

The current hypothesis is:
Someone before me wanted to install an auxiliary cooler and did a botched job, bought the cheapest cooler available (tube and fin) and bypassed the radiator. This has continuously caused the transmission to overheat because the tube and fin cooler cannot support cooling the transmission by itself, and is supposed to be supplementary.

I bought a plate and fin cooler and I'm going to route the cooler lines through the cooler in the radiator, THEN through the plate and fin cooler, and then back to the transmission. That should definitely get the cooling job done. I'll make sure to flush the transmission out and get good fluid in it. I'll let you know how it works!

 

Be sure to flush the cooler in the radiator as well.

 

What makes someone think they can bypass the radiator is beyond my understanding.

 

Some trucks come stock that way, but, they also have MONDO external cooler.

 

OK. Guess he didn't have a MONDO external cooler in this case. Or his MONDO external cooler had a bad case of cholesterol or sumpin'.

 

Indeed.