Speedometer will only go up to 40mph, and idea how to fix?

Speedo's can be fixed but it typically aint cheep and it really needs to be done by a pro. speedo cables are all short behind the IP...very few come out more than an inch or so ( if that) the idea being you undo it from underneath before you remove the IP.....IN assy they are put into the car already assembled and it depends on how far in the guy shoves it in and pushes the bendover on it....you can move them a little...but they will never come out far enough to unscrew them topside ( unless you have teeny tiny hands)