Ground wire problem

JD 5300, 1300 hours

About 6 months ago, it wouldn't start and since the battery was old, I replaced it with a new one. Started right up. But since then I've had an occasional problem where it won't start. After some tinkering around, what I found was if I pulled on the ground wire attached to the battery (negative terminal) it would start. I've cleaned and tightened everything several times but it still happens.

What I do is turn on the blinkers, then jiggle the wire until the lights come on and then it will start. It seems to me that the problem is at the end attached to the batter. It's as if the negative terminal in the battery is loose somehow. I've thought about taking the battery in to get checked but the problem is so intermittent.

Has anyone had this problem? Any ideas?