I have a 2002 Buick Century. After the car has warmed up and I'm driving steady on the highway between 60-70 mph, the speedometer needle will drop to 30-40 mph, bounce around there for a second or two then return to the actual speed of 60-70. Once this action starts, the needle dropping & bouncing around will happen at lower speeds when driving around town. One rainy night it actually dropped to 0 while going 30 mph & the car stalled. Not a good thing when driving up & down hills in the dark on slick roads. I've had the speed sensor replaced but the problem persists. Now the mechanics want to replace the instrument cluster. I do not want to have the dashboard taken apart to replace a part that might not fix the problem. Do you know what the problem may be and if replacing the instrument cluster will fix it? I really like the car and have only had it for 3 weeks.

Thanks, Bob

Optional Information:
2002 Buick Century V6

Already Tried:
Replaced speedometer module on transmission