Transmission issues?

ok, i have a 91 non supercharged ultra with 105k on it. Since I bought the car it had a rough engagment of the torque converter lock up. when it locks up, it makes a grind or even marbley sound. Inside it feels like someone put a sander on your car and turned it on. basically causing a vibration that is extremely annoying. If i keep the torque converter from locking up, the tranny is great and shifts great though all gears and shifts down nicely. so basically the lockup is rough and noisy. I have heard from some that the torque connverter is bad internally causing this and the tranny should be fine.. I change the fluid every 3K and it has a huge tranny cooler on it. Like i said the trans works ok and blows by people without a sweat. just the lock up is rough? Any help would be great, also where can I get them damn chrome trim peices that the ultra's have for the rear?

Any thoughts guys?? I must be the only car with this issue...

Any thoughts guys?? I must be the only car with this issue...
I have a '97 PA that HAD the exact same problem. An old transmission guy told me to buy some Lube Guard (gray and red bottle) and add it to the trans. Added a bottle and drove for 2-3 weeks, added another bottle and drove for 2-3 weeks, added a third bottle and 1-2 weeks later the shudder is gone. Car drives great, however, now I have flat spots on the tires...
Good Luck!