after installing new rear 10-12 bolt 2:73-3:73 no trans change but now it seems as though my speedo needle is alot slower?? it dose seem to be accurate about 3000-3200 rpm at 60-65 mph is this common after a rear gear change?? this was a big jump. just wonderin?? thanx Tony

Yes, your speedometer will be off now that you changed the rear gear. It's an easy fix though to change the speedometer gear. Remove the bolt by your speedo cable at the trans and pull out the gear. Count the teeth on the gear and go to GM and buy the correct one.........I'm not sure which one you need though.