What is this leaking part?

I hear ya... I hate ham fisted POs... There was quite a bit of red thead sealer in there too so he knows he messed up. The bottom of the rad on the drivers side is a mess and so is the skid plate so I think this has been a problem for quite some time. I put new transmission fluid and checked the level a few weeks back... only 2.5 quarts drained out!!!!!! Hope the tranny still has some miles left in it.

I would probably have been more enthusiastic to try stuff a few weeks ago but at this point I'll happily pay the $100 or so to get a new rad and be done with the whole mess a weekend and not have to worry about topping up the PITA sealed transmission. Besides, whatever torque spec is supposed to be on the fitting, I doubt it can be achieved with half the threads missing lol.

 

I Agree, I would also just get a new Rad at that price...

 

I Replaced The radiator the other day. Phoned around and found a Spectra Premium (SPI) radiator for $170. There were cheaper ones but Spectra and Denso were the only recognizable brands. I would have gone with the Denso but the guy didn't know how long it was going to take to get it. The spectra was available in an hour.

Some Spectras are supposed to be made in Canada but mine said Indonesia on the box. Not sure if that's better or worse than China. The unit itself looks fine on the outside. Plastic seems to be good quality. Welds are clean. Fins are straight. Don't really know what else to look for. The Spectra rad uses standard fittings and a lock nut to create a tight seal for the transmission fluid. No special fitting nonsense. The fittings also have some markings to indicate that they were torqued to spec.... good indication of some QC at the factory.

Took about 3 hours total.

 

After my second time around of having transmission fluid cross over into the coolant, and the dealer telling me to go fuck myself, I decided to eliminate the problem entirely. I bypassed the stock transmission cooler system and installed an aftermarket one. One of the best decisions I've made.
Went with one designed for a 30,000# tow rig, and now my transmission temps average about 140*F, and have peaked very briefly at 202*F. Previously I would average about 190*F, and once saw a sustained temp of 242*F (about 40 minutes!). And no more transmission leaks at, in, or near the radiator.
Something to think about if (when) you have another problem with transmission fluid at/in the radiator.

 

Glad to hear a happy ending to this. I was somewhat expecting to hear a pink / strawberry milkshake of doom story.

Very smart! I will probably do this in a few years when my truck turns 10 years old.