More about the toyota RAV4 problem

Thanks for the help. More details about the toyota RAV4 problem: 低速给油加速时，发动机转速增加声音增大但速度加得很慢，同时，车有膨膨响声. 速度超过 20迈加速没问题.  Also, at the beginning of starting driving, there is no this problem. After drive some time, problem comes. So, it seems that the problem is realted to temperature too. last time, 版主 biglow said it is possible "torque converter有问题". Please help whether temperature affect the performance make sense. I have dropped the car to dealer for further dianostic. But want to know should I change transmission oil and torque converter first? The transmission oil has not been changed for more than 3yrs (sorry that I forgot as I am a lady). Thanks.Amy