After reading many posts/threads about this on TW I came to the conclusion that a flush on my transmission with this many miles would not be a good thing.... I should just simply do a drain and fill on it.
However I came across this article/blog/post and am now asking for more opinions:
If you decide to change the fluid like you should, you cannot get all the fluid out by draining the pan. When you drain the pan through the drain plug you will only drain about 3 of the 15 total quarts. That is not much of a fluid change at all. Most of the fluid is inside the torque converter, transmission cooler and the cooler lines. Some vehicles like Mercedes have a drain plug on the torque converter so it can be drained, but not on our Toyotas. There is only one way to get all the fluid out of the transmission so you can replace it with new fluid. That is to flush it.
There seems to be as much bad info out there about transmission flushes as there is about synthetic motor oil. The number of professional mechanics that claim that a flush will blow out the seals and cause damage to the transmission dumbfounds me. Those poor people are suffering from invincible ignorance and refuse to understand the benefit of a proper transmission flush.
Here is the BIG secret about transmission flush machines. They do not use pressure at all. They use the transmissions own pump to move in the new fluid that displaces the old fluid and the old fluid is collected and thrown away. There are two basic types of flush machines and here is how they work and the differences in the two.
(S)he then also talks about when not to flush, eg when your tranny fluid is rancid, burnt and shot...
Since I don't believe everything I read on the internet I want to ask this question on the internet so I can read the answers:
Should I just drain and fill or get the transmission flushed? As far as I know my transmission fluid looks fine. It's just been a while since anything has been done to the fluid.