Ford - Taurus :: 2008 - Slight Shudder / Jerk When Put In Reverse Out Of Park

About three weeks ago I noticed a slight shudder in my 2008 Ford Taurus with app. 75,000 miles (automatic). It did not come from the steering wheel, but the car itself seemed to be shaking, but only slightly. Like someone who's had too much caffeine holding out an unsteady hand kind of shudder. It was going in for an oil change anyway, so I had my mechanic check it out, even thought the shudder was gone the next day. It came back, for a few moments while the mechanic was driving. He couldn't tell what was causing it, but said not to worry.

Two days later when I was in the car for the first time that day the car jerked when I put it in reverse out of park. I checked the transmission fluid, and, sure enough, it was about a quart low. All symptoms went away. I took it back in to double check that there was no leak and that everything seemed in good working order. The car was given the all-clear.

Then this week the shudder returned, again, only sometimes. It doesn't seem related to temperature, distance driven, or weather. And the maddening thing is that it only does it sometimes. I checked the transmission fluid again and it is still in the safe zone.

Two days ago, after being parked overnight, the car shook very noticeably for about ten seconds the first time I switched it out of park, first into reverse, then into drive. This was different to the other shudder (I know, seriously). This was a shake, like the bass in a super strong stereo was cranked. Then it stopped and the car drove just fine. I parked it for twelve hours then switched the gears again. Nothing out of the ordinary happened.

Today it had no issue when I first switched gears, but while I drove (for about a half an hour) that original slight shudder was there. This time at all speeds, not just low ones. I went where I needed to go, drove it again about four hours later and it was fine. No shudder, nothing and this drive went through road work with stop and go traffic as well as some time on a highway at speeds up to 55mph. I drove it another time after that, and again, no symptoms. Finally, I drove to the store. The shudder had returned. I parked, shopped for about 15-20 minutes, returned to the car, and it hesitated to accelerate as I pulled out of the spot. It did not jerk or seem to try to catch up. It simply delayed, but accelerated smoothly.

I parked again and let it rest for about 10 minutes, started it up, and no trouble at all. Even that weird shudder was gone. I think this car is toying with me. I'm taking it back to the mechanic, but the trouble is that it doesn't always have these symptoms. I drove it Thursday on a two hour trip and back again with no issues at all. This might make it difficult for the mechanic to diagnose, but at least it's a guy I trust. There are no warning lights on, no smells (unless they are faint as I don't smell things well), and no strange sounds.