2007 Yaris Shifting Problems

[dsanders337]

I looked around the forums and saw a couple of similar issues to mine, but nothing exactly like it.

My car is a 2007 Yaris Sedan with an automatic transmission and 103,000 miles. We've had it since it was new.

Starting a few days ago when going between 25 and 30 MPH the transmission shifts constantly from what seems like 3 to D if I have the selector on D. The tach fluctuates between 1200 and 2000 RPM when it switches. If I drop the selector over to 3, it stops doing it. If I then switch it back over to D it seems not to do it unless I stop completely and then start again. This seems to happen mostly on flat ground or slight downgrades when I am barely touching the throttle. There are no issues at lower speeds or faster speeds, and it comes up through the gears just fine on acceleration.

I want to try cleaning the throttle body and maybe MAF this weekend to see if that does any good. Other than that, I thought it might not hurt to get the transmission flushed since it has never been done. The fluid looks fine (pinkish) on the dipstick.

Any other suggestions you might have would be greatly appreciated!