Yes...shear bolt intact and the PTO clutch was not slipping (cold to touch). Everything from the pto to the top gear box, the side shaft to the final gear box was turning...except the actual cultivator blades. And they would turn when I lifted the implement...thus I believe the lower sprocket must be worn to the point where it won't take any load.
I really don't know what I am talking about so take this with a grain of salt. I wouldn't be surprised to find your tine shaft has a spline that splines onto the lower sprocket shaft. Wouldn't doubt you find that spline bad. May be a different connection altogether but I'm just purely speculating that is where you will find your problem.
Son and I were up this weekend and got into the machinery a little. Found a "machine key" that broke. It sits in a slot between the tiller shaft and the gear that turns it. Sooooo, if I can get a new key made, I think we're back in business!