So I had the Trans Failsafe Mode hit a couple of weeks ago. Turns out it was simply the plug connection at the tranny itself.

But I still have a weird shift happening at speed. Around 30-35, if I barely try to speed up, the trans will do what "feels" like a half-downshift. No noticeable RPM increase, but I swear I can feel it.

And, as soon as I barely back off the throttle, it "feels" like it shifts back up. Again, no noticeable change in RPM..

So, my question is this: The car has 133k on it. I don't know if the trans has ever been serviced. Should I do one?

It never seems to slip, or shift hard. Sometimes I get the 2-1 firm downshift, but not very often.

I did have the stealership update the software a few months ago. And, not sure it matters, but I put 20's on it around the same time. That's what the trip to the Dealer was for initially, an alignment that will maximize tire life.