I have a 93 190E 2.6 Sportline with 240,000 miles on it. The transmission seems to shift very well, although there seems to be a slight clunk when downshifting at a stop light. My bigger issue is that I tried to change the transmission fluid last week, and after 4 quarts, each quart I put in poured out of both sides of the transmission as fast as I put it in. I have just finished replacing the pan gasket thinking it might be the problem, but I still can't get more than four quarts in it. Any ideas what the problem might be?

Thanks,
Jason