My Cadillac CTS (5L40-E trans) has a little over 115k miles, and the auto trans has been getting better over the past two years since I bought the car. Specifically, it had what I called loopy, or otherwise erratic shifts, which were worse when the trans fluid was cold (much like the symptoms of low ATF level, but I verified the level was fine). I don't know if these are actual "transmission flares" but they consisted of a surge feeling upon upshifts, and inconsistent or oddly timed upshifts while coasting or light pedal. My first thought was that this issue was caused by the high mileage, but I also noticed it in my friend's Ford Focus with 45k miles. My first approach was to have the ATF replaced at a local shop (they probably used NAPA Dexron VI, given the shop's affiliation). The shifts did not change, so I dropped the pan, replaced the filter, and replaced the lost fluid with Valvoline Dexron VI. The shifting improved a little, but was not what I considered normal. My next step was to add a bottle of Lubegard red. The upshifts became smooth and normal during acceleration, but the weird coasting/light acceleration issues remained. It was almost as if the car was trying to get to the highest possible gear, regardless of whether it was time to do so. In other words, if i accelerated to the point of a downshift, and then backed off around 2500 or 3000 rpm, it would shift back up, and then immediately shift up again, only to shift back down to maintain around 1500-1800 rpm cruising. After about 4 months since Lubegard, this issue hasn't changed at all. Today I decided to try Seafoam Trans Tune, which I had used previously in my power steering fluid (with little to no effect on steering performance; however, a friend in college successfully used it to fix a slipping trans). I suspected the outcome would be A) trans tune would do nothing, B) trans tune would completely solve the shifting problem, C) trans tune would completely F up my trans, or D) trans tune would cause ATF to leak all over my garage. The preferred outcome is B, but A would be acceptable. C or D would be bad. I am happy to say that Trans Tune was effective within a few miles, and the trans now shifts great during acceleration and cruising! I haven't tried it with cold starts yet, but I am optimitic. I will update this thread in a few weeks with any changes to the shifts, etc.