having problem with my'71 speedometer,trans gear and cable were replaced during resto (cable well lubed).since the first time i drove car,needle registers ok to about 40mph,after that,needle jumps into 80,90,and 100 range.i didn't take cable out yet,thinking it would correct itself with some miles...no i suspect gear in speedo is damaged if so what's involved w/repair....thanks folks,jc