Oldsmobile/Buick Repair: 2000 buick tranny, buick lesabre, upshift

Question
I just bought a 2000 buick lesabre 2 weeks ago with 80000 miles. Yesterday after driving for about 20 minutes it started to shift very hard. especially from 1st-2nd-3rd, the shifts were hard accelerating and decelerating. It was also making a whining noise just before a hard upshift into 3rd gear. It only happened this one time, drove 26 miles to work this morning with no problems.
Any Clues? I still have lemon law coverage on the car but since the problem only happened one time I am afraid the dealer won't be able to replicate the bad shifts.

Answer
Hi,Jim
Sounds like the transaxle pressure control solenoid is failing,also the valvebody inside trans may have sediment and is restricting valve movement,there is a GM bulliten for your complaint the number of the bulliten is 901351,and lists your exact complaint.
 You will need to have the dealership perform the diagnostics and repair,and refer them to this bulliten and they will be able to repair your trans problem.if you need any further help contact me,Thanks


ED