Hopefully this part exists or someone can tell me, what trips the fail-safe on the transmission to disabled o/d and TCC? I believe I've heard temperature 260+ does this, mine is infact in warmer weather tripping the fail-safe. I'd like to replace the sensor (if applicable) along with installing my external transmission cooler.

The temp sensor is located inside the side pan of the transmission. Not the bottom pan, but the dreaded side pan which requires partial removal of the transmission to get the side pan off.

From my 4T60-E ATSG manual...

Damn, there'* always been two stored codes but I think it was for lockup, forgot the other. I don't have someone with a scanner anymore, and don't feel like paying $80-$100 for a simple scan to get history codes. Crap.

That coolant temperature sensor you are talking about it falls back on, is that the one at the lower intake IIRC? Does that also happen to be the one sending to the gauge readout? I remember the heat sheath came off of mine a year or two ago, but the temp is always very low in my car, I have AMSOIL coolant and a 180 Intense t-stat...

Yes, the temp sensor sits just below the upper radiator hose housing.

The PCM takes the temp and forwards it to the instrument cluster. If you were to disconnect the temp sensor while the engine was running, the PCM will automatically turn the cooling fans on LOW as a precaution.

This is what I have and will be installing in the next week or so (whenever I have a damn minute):
My other thought is, can my trans really be hitting 260 considering I don't notice anything ever wrong and the fluid isn't burnt? It does only happen on days 80+F out. My other thought was, if this trans cooler doesn't alleviate the issue, cutting the trans temp feed to the PCM so it falls back on the engine one and hooking up a gauge pod with trans temp. Thoughts? Ideas? Opinions?

Honestly, I think you should find a way to verify that your trans is indeed getting that hot and actually tripping no OD.

Thanks for the info, will be testing that. It'* possible it'* sending the wrong resistance...