i was wondering what could cause my speedometer to be wrong, cause i was messing around and racing my friend in his 86 firbird and his speedometer goes to 85 and we were going pretty fast when i talked to him later he asked me how fast i was going and i never went over about 90 or so mph but he said that his speedometer was all the way back around to 15 mph so im wondering could the fact that the posi is out on my 2.77 geared rearend cause my speedo to mess up like that?? plus when im accelerating it jumps around alot it bounces back and forth a good bit what could be wrong and how can i fix it???

Thanks -Don

 

Probably the speedo cable needs some oiling.