I sent Toyota and email regarding this question, from their web site. here is the following response that I got ( I edited out my real name....)
Here is the question I asked them in the email .......
"I have been told by my dealer that I should get the auto transmission power flushed rather than having the oil drained and filled which I do every 30,000 miles. It does not state in the owners manual that power flushing is required and many auto experts I have talked to tell me that power flushing a transmission can cause problems. I personally have had 2 vehicles ( not Toyotas) that developed transmission problems very soon after power flushing them, and for this reason I prefer to drain and fill every 30,000 miles.
I would like to know Toyotas official position on this issue. "
And here is the answer that I received my Email
" Dear Mr. **********,
Thank you for contacting Toyota Motor Sales.
We appreciate the opportunity to address your concerns.
Fluid flushing is not a service/repair recommended by Toyota. In terms of maintaining the integrity of your warranty, Toyota Motor Sales' primary interest is adherence to the Scheduled Maintenance Guide.
Your local dealership may recommend more frequent maintenance intervals or more maintenance services than those listed in the Scheduled Maintenance Guide. These additional services are not required to maintain your warranty coverage. We recommend consulting with the Customer Relations Manager on site at your local dealership for an explanation of any recommended maintenance not included in the Scheduled Maintenance Guide.
Thank you again for contacting Toyota and for the opportunity to address your concerns.
If we can be of further assistance, please feel free to http://www.toyota.com/help/contactus.html.
Toyota Customer Experience "