CRAFTSMAN tiller model# 917.296010 tines not engaging

Randy, The gear in the gear box may have sheared a key, or damaged gear. Check the attached links,instruction and guides, Good luck
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Tiller Gearbox Trouble
Murray Ultra Tiller Tines Won Keep Spinning
Update Craftsman rear tine tiller repair stuck gears

You probably have a belt drive that has is not tight enough to pull under a load. The belt is pulled by an idler pulley that engages when you start the tines. Check the belts by working you engage lever and look for the belt and idler. More than likely there is an adjustment that will allow you to put more tension on the belt thus making it till. Do not do this when the machine is running! The belt should not have flex in it when engaged. It may a little effort to engage the tines when you get it tight enough to till.
Col. Dana Gillespie

model number would be VERY helpful here because craftsman made many different styles/models throughout the years

It appears that the gear case on your model is not capable of being serviced. The cost is over 300 dollars. There is a shear pin or similar connection in the case where the shaft connects to the pulleys. It has broken off and the shaft has no torque now.

There should be a spring on the other end of the engagement cable connected to the take up (idler) pulley. It sounds like it have broken or came off. You will need to removed the side cover and inspect. After you have the cover off, pull the engaging bar and watch the take up pulley for correct operation.

That is correct "Only if the shifter cable isn't broken!" And if it is a linkage type, make sure all of your clevis pins are in place. And on mine even if i get it in gear...the "dead man" is cable connected for sure. Make sure when you squeeze the "safety stop" or "Run/engage" lever that it is actually moving a lever at the other end. If so? Then trans box is next to inspect. But that would have had to suffer a nasty jam to damage that. And again with other people I've seen this a hundred times with rear tine tillers. Sometimes it just "cogs out" into a state of "bad mesh" with the gears and all that is needed is to push or pull the tiller a bit while you try to engage the shifter. The wheels just got be rolled a tiny but and "Voila!" you've managed to free up the meshed gears to a state of freedom. Sometimes its that simple!

Tines only spin in the T position.with cutch engaged.If thats not it split the case and check to see the shift fork operating properly. Or that chains are not broke. NOTE This is a serious job!!!

It sounds like the belt just stretched. Now you need to move the belt tensioner over to put more pressure on it.

tilt the back of the tiller up and check for a rock or stick wedged in between the tines and the shield

Sounds like the worm gears are worn to the point they will not engage.