I was driving my car earlier today(which has never had any problems)and the car was shifting way late from 1-2,and when it finally did shift(at around 3000-3500) it shifted very hard, almost chirping the tires. Then when i drove it home it worked fine, but the same problem occured later that night for about ten minutes after that it drove like normal. Does anyone have any ideas as to what is wrong...i checked the fluid and its fine. If it helps the car 120K miles on it and is an 89 GTA with a 350 TPI in it.

 

Your Throttle Valve is sticking. This is one of the primary reasons for a 700 failure. If it sticks in the low pressure position you get slippage.

 

The Trans-Go Shift kit Junior will solve this as transfixleo said "your throttle valve is sticking", this kit will solve "the sticking TV problem", if you want more than just the problem solved, let us know we can be of help!