Tranny Gurus needed.

[mike_dmt]

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.

[bbultman]

Could be a torque converter locking/unlocking. When my X5 is cold, I get like a three step mini-rpm bump up before it shifts then the cycle repeats until I'm over 60 mph. Once it's warmed up, light throttle from 30-60 gives this misfire-like blip every 2 seconds. Found out it's the torque converter locking/unlocking and you can just see the tach blip (about 25-50 rpm). Very minor, almost unnoticeable. If you put it in cruise control, it goes away because cruise locks the torque converter. You can test that. Got all concerned about it until I talked to ZF engineers and they were thinking more along the lines of the valve body but didn't rule out ailing TC. If the TC valve pressure is not quite high enough, it can act like the above. That was 25k miles ago and it hasn't gotten any worse and has always shifted great. My prediction is likely a pressure issue in the valvebody. If anything, you could do a pan drop and filter but I would not do anything else.