Craftsman 917.296040 Tiller does not have any gear selector tension. Where and how does the gear selector connect to the cable? What is wrong here?

Here are some possible causes and solutions:

Belt Issues: If the drive belt is broken or loose, the tines won't turn. Check the belt tension and replace the belt if necessary .
Idler Assembly: If the idler assembly is not properly tensioning the drive belt, the tines won't turn. Adjust the idler assembly or replace it if necessary .
Engagement Cable: If the engagement cable is loose or not tensioned properly, it may need to be tightened or replaced altogether .
Transmission Issues: If there is an issue with the transmission, such as a broken gear, the tines won't turn. Stop using the machine immediately and inspect the transmission .
Since you mentioned that your tiller tines were turning fast after replacing the carburetor and then stopped turning after connecting the throttle cable, it's possible that there is an issue with the engagement cable. You may want to check if it's properly tensioned and connected to ensure that it's not causing any issues How To Fix Tines That Will Not Move - Tiller Repair

look for the bolt , upper case of the tranny

Go to sears.com. at top of page about center of page find parts. put in model #. It will give you a breakdown of the whole tiller.
R.G.S.

Try adjusting the linkage or the shifter cable. If its too tight that will happen. I have almost the same one you do. Look at your manual and check out the blow up diagram. there is a way to adjust most models. If not you may need to replace the cable. But...before you do that make sure your cable isn't meeting with resistance somewhere causing it to be too tight.

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!

It will be rather difficult to explain how to do this properly in text, but what I can do is give you a couple of pointers. The first thing you need to do is set the range by putting the deraleur to the highest gear (smallest sprocket) and checking the cable tension when your gear selector is also on the highest gear. The tension should be ever so slightly tensioned, but not sagging. First screw in the little cable thumb barrel adjuster(s) all the way in and then 1.5 turns out. Then adjust the cable as described above and secure. After you've done this, put it in first gear (biggest sprocket). It should go there with verve and confidence. If it does not, you need to tighten the cable some. (Do this at this point with the little thumb adjusters along the cable.) Try again. Go through the gears. The indexing should plop the gear to the next lowest accurately and without hesitation. If the chain clatters in any one gear, the indexing is off, and you have to loosen or tighten the cable. If you tighten and lose the ability to put in first gear and fifth gear yields a really loose cable, you went the wrong way. Instead then, loosen the cable one gear change's worth. Or... if you adjust the cable and it goes into first but you lose the ability to access the highest gear, the cable is too tight and you went the wrong way. Loosen it one gear's worth. Now at this point, you will just be diddling with it until the shifting becomes accurate. Be patient and hone it in to the best performance. (I assume you lubed the cable before putting it in.) Hope this helps.

SOUNDS LIKE THE BELT HAS CAME OFF OR THE PULLEY HAS BROKE

I would check and see if your cable is binding. If it is binding you may not be getting it engaged all the way. Also you have to rock the tiller back and forth a little while you are trying to engage it or sometimes it will not engage all the way and then will pop out. Also check that the arm the cable connects to at the transmission is free to move in and out of gear. Sometimes those get coroded up. Just spray some penetrating oil on it,the cable and lthe lever. As far as I know there is not a tension adjustment on the cable.

Good Luck!

find your model number from the list on this link and click to get your manual

http://www.managemyhome.com/mmh/owner_manuals/search?query=Craftsman+rear+tine+tiller

that is gears