It is a 97 Ford Explorer Sport with automatic transmission. Occassional I experience a thud and RPM's drop to nothing for approximately 1 second. When it has happened I have usually been driving 65-70 mph on the highway. It does not always happen when driving that speed on the highway, just occassionally. I feel it, it has the feel of rapid breaking, but just for that split second. Sometimes it will happen 20+ times in the course of a few miles. Other times I will drive 50+ miles without it happening at all.
Vehicle has 180K. About a year ago I did start noticing that the transmission would "slip" (I think that is the correct term) when I would try to accelerate quickly from a stop. If I accelerate hard from a stop, I may hit a point where RPMs fly up but the vehicle is not moving at that speed. Net effect it has caused me to actually drive less aggressively. With regular everyday driving I do not experience any "slipping".
I suspect the two may be related. Any ideas?