I bought a 2015 RX  F-Sport-- with around 79,000 miles from small dealer. A week later it started downshifting and jerking after driving for over and hour with transmission oil hot.

I found out previous owner had torque converter replaced at Lexus before they traded it in.

I had the transmission fluid exchanged at my local shop and the problem seems to have resolved itself.

My mechanic said Lexus didn't replace the transmission oil when replacing the torque converter which is what their own protocol is supposed to be.

Thinking about trading it in for a highlander with 6 speed automatic. But, have not had problems since. How reliable do you think the 8 speed transmission is?