If you get one and it shudders with new fluid or klangs when you first start it up, it is most likely bad. Klanging on startup in a classic sign of converter failure. The clanging will subside after a few seconds then it MAY run ok for 10-20 miles then start shuddering. Even if you change fluid. Converters are NOT supposed to do this. Some people had a vibration. Mine had a NASTY shudder that you could feel in the floor and hear coming from right beside your right foot, right where the converter is.
Try a 12" higher stall. 2600-3000rpm. Anything over 3000 rpm and it will severely affect driveability. There is a torque converter manufacturing facility about 15 minutes from my home that I consulted with. They are the ones who built the converter that is in my truck now.
My 9/11's driveability sucked because it had failed on startup, slowly dumping metal into the valvebody, cooler, and tranny. They are not all bad. There are those of us that did get bad models though. The more of something is sold, the more likely you'll find bad ones. Just the way manufacturing is.
The price crept up over time supposedly due to increases in the quality of parts used in the manufacture... :roll: ....Brian wrote on here somewhere that there was a release spring/washer that was deleted in the design of the old 9/11. Very well may have been responsible for the VIBRATION people feel at certain rpms.
Don't know if this helped explain the difference well enough between vibration characteristic of the 9/11 and the shudder of a bad converter(not just a 9/11...any converter).
Blake