722.6 w202 tranny reved like in neutral while driving during atf change

[White951]

I got around to changing the atf today and drained a little over six liters out of the pan and torque converter. I added five and a half liters and took it for a drive to warm up the fluid. I went from about 10 mph to a sweeping on ramp doing about 30 mph and at the initial turnin on the ramp the motor all of a sudden revved like it was in neutral. I coasted to a gas startion and turned it off for a minute. After turning it back on I put it in reverse and it was good in reverse. I put it in drive and it was moving but would not shift out of what ever gear it was in. I drove going slow to over rev the motor to where i could stop again and pull over. I turned it off and waited a minute. I looked underneath and everything was good underneath. I started it again and it drove away fine shifting through the gears. After getting it home and getting the pan temp to 80'C I put another 1 and 1/2 liters in and checked it with the factory dipstick tool and it was perfect on the dipstick. What could have caused the revving on the drive and is this the sign of a problem? I'm hoping because it was still down over a liter in fluid that maybe these tranny's are sensitive to fluid leves. Hope nothing is wrong. By the way its a 1998 C230 and its got 120K miles on it purchased at 58k and never shown any tranny problems.