1995 Buick Century hesitation..

1995 Buick Century 3.1 with 130k miles on it hesitating bad as vehicle shifts into overdrive. If I run the car on 3rd gear it seems to alleviate the issue although when stopped at a light and drive vehicle bucks pretty hard.

Any idea if it transmission or motor related? Where should I start...

I have no history information on the vehicle, just bought it 3k miles ago and it has run very well up until now....

Anticipated Thanks....

Welcome to AF.

Since the vehicle history is unknown I would look getting a basic tranny service. Pan drop consisting of ATF (Dextron-III) and the screen filter. I would not get a flush service with your mileage.

Also, if you live up North it could be affected by the cold weather.