Car Stall Problems of Lexus RX

When driving my Lexus Rx 300 1999 it feels vwry forced and when on the express way the rpm goes up to 5 when im driving 60mph and when I come to a complete stop and its time to go my car stalls as if it was in neutral very scary when I have my newborn and a 7 year old in the car. I have maintained my car to the upmost standards from the best gas synthetic oil changes constantly checking everything is in good conditions . For a Lexus I am very upset because my mechanic has said its the transmission and that I will have to replace it which costs 4-5,000 dollars and I mean is a 15 year old car worth putting 5 grand into it? I expected this car to last me a little bit longer I mean from what I was told this car should go to almost 300,000 but its obviously not. I am very disappointed that a Lexus would have this common problem from what I've seen and read.

See all problems of the 1999 Lexus RX 🔎.