Automatic Transmission Cooler problems of the 2008 Lexus RX350

After having to replace brake calipers, a broken key, and the engine oil cooling pipe (warranty) in the last year, my RX 350 is having transmission shudders with 136k miles. This is ridiculous for a car with the Lexus name and price. The car is hesitating during shifting causing issues while driving. I have not had to replace the transmission yet, but with the reviews for some older models, I fear this is coming soon. I am very disappointed to pay this much money for a quality car that is supposed to last 250k+ miles, and having so many problems with just 136k miles on it. It does not live up to the Lexus quality reputation!.