Speedometer problems.
 

Hey guys I'm new here seems like a great site! The problem i have is with a 94 850 non turbo, and when i start driving the speedometer sometimes will not move and it wont shift and sometimes it will other times it accelerates fine but if i hit a bump the speedometer drops down to 0 mph and the engine revs like crazy. I'm really stumped and i don't know what to do? If i wasn't clear about the problem ask and i'll try to explain better.

Thanks guys,
Justin.