i have a 1995 525i with an automatic transmission. the car had a rebuilt transmission installed at 117,000 miles and has 172,000 miles on it now. my wife mentioned the transmission was not shifting smoothly and i changed the fluid and filter. the transmission works fine now except right after it shifts into third gear there is a rumble and vibration, then it smooths out and shifts fine into fourth. the transmission shifts at 2000 rpms under normal driving. if i shift the car manually at 3000 rpms i don't notice the problem. are there more servicable parts on this transmission? should this car shift at such low rpms? am i heading toward another transmission?