well i was going to school andi take the highway and i was going with traffic well i look down and my speedo say 50 and it wont do higher. my car runs fine and when i slow down it goes back down but when i speed up past 50 the needle sticks at 50. why? how can i fix this? is it a cable or computer controlled?

It should be PCM controlled, but the gauge itself may still have a mechanical binding. The signal comes from the VSS in the trans, is processed by the PCM (counting pulses and comparing to time), then the signal is sent as an analog to the gauge. You may have a chunk of gunk in the gauge. I can't imagine a scenario where your PCM stops processing the digital pulses at 50mph.

my pcm is about 2 years old or so. should i take the speedo cluster out and what should i look at and for. does the gauge even open up?

what do u mean "what fun" is it gonna be a hard job?

take the dash abart is no problem to me. so u guys think its a mechnical problem.

Is the gauge face starting to de-laminate causing the needle to bind? Not famillar with the buick speedo but is 50 mph at the top of the gauge?

yeah car still shift in to OD at 45- 60 depends on how im driving. here is a pic of where 50mph is at dont forget my gauges are much different looking then ur bonneville.