Craftsman Lawn tractor DT 3000 Model

I'm not quite sure what you mean by the shift lever ... does that control the speed of the mower or is it to make the blades work? I wonder if it is your clutch cable? My spring broke that engages the blades. It is a long cable that goes from the lever to engage the blades down to the deck. The handle to engage the blades will not have any tension, it is just loose. See if the spring is hooked up properly on the deck, it might have broken but looks like it is still all attached. The videos on youtube and also repairclinic.com show how to replace them.