Thank you for using Just Answer for your needs. Did you check the codes yet?
Did you get the infamous code P0773?
Thanks. These codes have been common for some time and replacing the solenoid will not fix this concern. The P0773 code Shift Solenoid E is what the repair manual calls the SL solenoid and is used for torque converter lock up.
When the torque converter is locked the computer monitors the RPM's produced by the crankshaft sensor and compares it to the Revolution sensor on the transmission. Since the engine and transmission are 'locked' by the SL solenoid and torque converter then the computer looks for a 1:1 ratio of revolutions. When it doesn't see it, it sets the P0773 code and turns the check engine light on.
The real problem is in the torque converter itself and depending on the Avalon mileage, you will want to consider the transmission also.
But if you still want to try replacing the solenoid then it is easy. Drop the transmission pan and when you see all the solenoids, look at the one closest to the front bumper and also closest to the engine. That is the SL valve.
Is there a chance that changing Solenoid E will fix the problem, or is that just a complete waste of time?
We have replaced them before at the customers behest and none have ever been fixed by replacing the solenoid E.
To replace the Torque converter, you will have to pull out the transmission and hang the engine. This is not something even the skilled owner will want to attempt and is better left to a Professional Repair Shop. As for cost, it will run about $900 to replace just the torque converter but with 150,000 miles, you will want to consider installing a new or re manufactured transmission. That would run $1,800-2,600 depending where you get the work performed.