Transmission thumped under acceleration and lost all but first gear.

What is your question?

First gear will not work in DRIVE but will work in the 1 and 2 position. Reverse is also out. The car has about 160,000 mi on a rebuilt, updated Delco trans. I was accelerating on a freeway ramp when the thump occurred followed by the engine free revving while the trans was in the Drive position. There was also some smoke under the hood though I could see no leakage, and the trans fluid level was good.

What makes this problem better or worse?

Nothing I know of.

How long has your 1993 Buick Park Avenue had this problem?

Started this morning.