Slips at 70mph

[Bigbl5]

I have a 99 Explorer Eddie Bauer 4.0L SOHV 4WD. Yesterday while driving down the highway, the truck felt like it dropped out of gear for a second then kicked right back in and "jerked." It did it a couple for times within the next 2 miles, so I got off the expressway. It shifted just fine at lower speeds. Then later last night I went down the expressway again, and didn't have any troubles... My truck has 216000 miles. Any thoughts on what the problem is besides just "transmission?"

 

[BubbaFL]

Could be the torque converter unlocking then locking back up?

When's the last time you changed the transmission fluid?

I had a problem like that with my wife's Windstar; changing the fluid fixed it.

 

[boominXplorer]

Is your O/D light flashing? Sure it wasn't a low throttle miss-fire?

 

[Bigbl5]

I don't know if the trans fluid was ever changed. I did check it and it was full and didn't look burnt, but it was a little on the brown side. The OD light was not flashing. In fact that was the first thing I checked... I turned the OD off and it kicked down in gear and the rpm's went up. I doubt it was a misfire as it felt as if the engine was still running...more like it just popped in neutral.... but the engine did NOT rev up when it slipped...does that sound like a misfire?

 

[Bigbl5]

Its been over a week since I had the issue with "slipping." I'm going to venture and guess that the misfire diagnosis was the likely problem. I used some fuel injection cleaner in a new tank of gasoline and have not had a problem since. I've driven several hundred miles on the expressway all the way up to 80mph and have not had a repeat of the problem.