Hello everyone! It's been a long time since I've been on, but I have an issue that's kind of stumping me.
It's a 2010 Corolla S, automatic, with 130,000 miles and been in a semi-major front end accident a few years ago and repaired.
A few years back, I came to the forum asking about hard shifts. It was recommended that I perform a few drain and fill style ATF changes. I did four or five of those over the span of 30,000 miles so I could cycle out as much old fluid as I could without doing a flush. The shifting seemed to get better so I chalked it up to a success and went on with life. Over the last year, I've noticed the rough shifting coming back little at a time. Recently, it's become quite noticeable and actually starting to concern me. From a stop and accelerating from 1st, 2nd, 3rd, and OD, all is well and no issues. The issue is with downshifts from OD to 3rd or 2nd, especially when I need to pass someone. I will give a decent amount of throttle and it drops out of overdrive and waits... Then shifts into second. Almost like it missed third gear altogether and went to second. On the times it does find third, it lands into gear pretty hard and you can feel it jerk into gear. The concern is not only that something is wrong, but it's also starting to cause a safety issue. I'm not an overly aggressive driver, but if I see an opening in heavy traffic, I'll punch it to merge in. I've had the downshift hesitate long enough that the spot in traffic that I was clear to enter without any issues now has traffic bearing down on me with quickly and I'm stuck with puny acceleration until the car wakes up and downshifts.
This issue isn't constant and I can't always recreate it. Some days it drives like a brand new car and other days it seems like it's time to trade her in. I checked my ATF this morning and I noticed that it was a little past the full mark when hot, so it could be overfilled, but not by a whole lot. I also noticed that it wasn't shiny red on my rag when I checked it. Not brown, but more of a maroon color and did not smell burnt. I could drain a little, but I'm not sure that will make a difference.
I will mention that I'm running the original spark plugs. That seems like a random comment and I know I'm way overdue on changing them... But I started to think that maybe a general lack of power due to old plugs is causing an issue where the transmission is making up for the loss by shifting me back an extra gear when in normal conditions it wouldn't do that?. I'm honestly not sure. Any thoughts or suggestions would be welcome. Thank you!
