Pontiac Repair: 1999 Grand Am, spining wheel, best bet

Question
4 cyl,117,500 miles; auto trans shifts hard into 2nd and sometimes 3rd when it has been driven about 60 -70 miles. Then the "Trac Off" light comes on,  BUT it only does this SOMETIMES!  Aamco could not get it to do it today and after they failed I drove it about 100 miles and it only had a very mild lurch when it shifted into 2nd.  Aamco said to drive it till it happened again and come back in. I'm afraid to do this and take a chance on destroying the transmission,  HELP!
 P.S.  What is "Trac Off"?

Answer
You dont need to worry about destroying the transmission. What is happening is that the computer is seeing something wrong and then commanding the transmission to run at full line pressure. Thats why it shifts hard. It could be a bad pressure control solenoid or one of the shift solenoids or about a hundred other things.
The trac off light means that the traction control is being turned off due to a problem. Traction control is part of the anti lock brack system. If you take off from a stop and the wheels spin, the traction control helps stop the tire slip by either partially applying the brakes to the spining wheel or by retarding the timing to lower engine power and torque.
Since both problems happen at the same time, there might be some codes stored in one of the modules that will help in diagnosing the fault.
Your best bet would be to take it to the dealer to have it diagnosed instead of just a tranny shop. Most tranny shops dont know about how all of the cars systems are tied together, all they know are transmissions. The fault may not be in the transmission, just the symptom that you see(the hard shift). The problem could be in something that has nothing to do with the transmission.