2000 Tundra 4x4 bad transmission

The transmission in my 2000 tundra is on the way out and I am going to replace it with a used one. The truck has 200k miles on it. It developed a weird vibration 50 mph and up. It wasn't a strong vibration...you could just barely feel it in the floor pan and more or less hear it. After ruling out driveshafts and front and rear differential I confirmed the transmission was bad after dropping the oil pan and finding bits of metal and a lot of brass/copper.

I will be putting a transmission in it from a 2003 tundra that has 102k miles. I will be replacing the transmission filter and doing a flush on the system prior to installation. Is there anything else I should do? I am halfway thinking of replacing the input and output shaft seals and maybe even a completely new transmission cooler. Anything else that I am missing or should do? Thanks for any help.

 

Maybe the radiator if it hasn't been done? OEM, Koyo or Denso replacement.

It has the warmer/cooler part of it that can fail. Plus at 20'ish years old its plastic tanks are nearing the end of their life.

 

I replaced the radiator at 175k miles when it failed. Thanks for the suggestion though.

 

No problem.

Instead of a pressurized 'flush', just do several drain and fills. Valvoline Maxlife seems to work good.

 

Update

I have the old transmission out but I left a plug connected and pulled the wires right out of the connector for the transmission temperature sensor. I have no idea which wire goes on which side (2 conductor plug) but I am thinking it will not matter since it is a thermistor type sensor and polarity should not matter. Anyone have any thoughts on this?

I also need to swap the transfer case adapters due to the replacement trans having a broken bolt. Is this going to be an issue swapping them out due to them having a bearing inside?