Leaking issues in my 200 4R - any gurus available?

Mine has a non lock up also. I run my fluid through the radiator then through a cooler. It never ever gets above 185 degrees. But I have a temp gage also. If you suspect overheating all you have to do is get a cooler with good fan attached, that will really bring the temps down. But i don't think that will solve your problem because something must have happened when you changed the fluid/filter at the beginning of this thread?? Also, you wrote that it only happens at higher speeds (not in city streets) so what happens in the transmission at higher speeds (loads) that doesn't happen on city streets??
First check the dip stick seal and let us know what you found. Hang in there!!

treblig