the speedo cable on my son's 69 broke the other day. we bought a new one from the local auto parts store. It was longer about 79" but looked right. the one we pulled off was like 59-1/2". It didn't make it a mile before it broke. I figured it was in a bind because of the excess length. took it back and got the only other one they had 63" put it in and it didn't make it a half mile before it broke. the gear on the trans end looks fine. if I take the broken end of the cable and put it in a drill it turns the speedo freely. what the H*ll am I doing wrong ? 351W FMX 3:00/1 gears.