Instrument Gauge Swap

I have a '90 xj that had the useless gauge cluster on it and decided it was time to swap. Went to the junkyard and found a cluster from a '86. Pulled the cluster and speedo cable. The first night I put the cluster and the donor cable in and forgot to tighten the speedo cable to tube it rides in and the speedo didn't work today. Quickly realized my mistake and fixed it but now the speedo jumps. Anybody know why? :dunno:

the speedo in my '87 jumps untill I get over 50mph or so.. I figure the cable needs lubing..