The fluid lines are ran the right way. The throttle valve cable does have some slack, but it's not sticking. How would you adjust it?

Do you still have the check valve in the cooler line?

No. That's been removed.

If it's not blockage in the cooling system I'll be very surprised. Were it mine, once that issue is resolved I'd change out the ATF, all of it and not just what falls out when the pan is dropped. By the time the idiot light comes on the ATF is hot enough to have formed varnish and you'll want fresh oil in there to get that varnish lifted and filtered before it can cause serious problems.

If it's blockage, it must be in the radiator. It's got a new cooler, and lines. I'll check that out, and see what happens.

What year is the truck, and what year was the trans you put in?

The truck is a 99 dodge ram 1500 4x4 with a 5.9l. I drove the truck about a year before the tranny went out. I bought a 2000 dodge ram 1500 4x4 with a 5.9l for parts. Pulled the tranny out of it, and put it in mine. It went out the same way that the original one did. This time I got the tranny out of a 99 dodge durango 4x4 with a 318. I replaced the lines, and intercooler this time, and mounted the cooler at the very front. This tranny is doing the same thing the first two did. ???

The 2000 trans was an electronics mismatch. The 99 'rango trans, I am not sure..... still and all, flush all your cooler lines, see what happens.

I'll flush everything, and update this after. Thanks for the help everyone.

You guys have been a lot of help, and I really appreciate all the great advice. Did the flush, and there was definitely blockage in the radiator. No more Trans Temp Light, or OD/OFF light. Now the problem is that it doesn't want to shift into overdrive until I let of the gas. Sounds like a sensor. Any ideas?