I recently put in a new th350 from TCI , got everything hooked up filled fluid cycled through gears and everytime i get to 3rd it relieves pressure blows trans fluid and a little coolant. What is going on to cause this ????

The only way I know of for a transmission to "blow a little coolant" is if the cooler in the radiator is bad, that is the only place where the transmission could encounter coolant....

Damn that is rough...

Time for a new Radiator, Transmission-cooler, Transmission, and Torque-Converter.

I am very sorry for you loss.

Wait. The transmission pressures should be far greater than the coolant system pressure.
Therefore there should be no coolant in the transmission / torque converter.
Just trans fluid in the coolant. Correct?

OP - does your trans dipstick show a strawberry milkshake?

Not getting coolant in the trans no its pushing around the trans cooler line connectors I think that they didnt seat well is all. Everything is new trans, radiator, and convertor. would a missing vacuum connection cause excessive pressure ?

Since your transmission pressure, even in the transmission cooler lines, is much higher than your coolant pressure, a slight cooler leak very well could pressurize the cooling system to the point of forcing coolant out of strange places . You say you have no coolant in the transmission, great!, BUT, are you SURE you don't have any transmission fluid in your coolant?

Yes... but the coolant can enter the Transmission-Cooler in the Radiator when the engine is off and the vehicle is sitting.

Agree 100%, when the warmed up engine is shut off and the transmission fluid pressure goes to 0 the radiator is still pressurized at 15 ish PSI, with a bad cooler one would think that both fluids would mix in both the cooling system and the transmission.

Good point.