My Craftsman DLT 3000 Riding Lawnmower will not go into gear.Could something have come loose? a spring orwire to the mower?

Carb needs cleaning and possible rebuild. Very common problem especially with ethanol gas.

Try this : http://www.ssbtractor.com/wwwboard/view_all.cgi?bd=lawn&msg=12041 or this: http://www.manualslib.com/manual/496601/Craftsman-917-272440.html

cable is broken down by the deck... most likely
or it is broken by the handle... also most likely
belt engagement arm is stuck... also likely

The transmission drive belt is a separate one from the blade belt. The clutch pedal when released puts tension on the transmission drive belt so it tightens up and drives the gearbox pulley by way of a large spring. Make sure the spring is ok. The belts don't last forever and probably needs replacing looking at the age of the machine. That is a fun job as it is right up under the machine and runs from the engine pulley right back to the top of the transmission. You have to drop the deck right off and I usually find a tree with a large branch and haul the front up with a rope or winch so the mower is vertical. Makes it easier to work on. Drain petrol first though. Hope this helps otherwise get a mower shop to do it for you if you feel it's to much of a task. Good luck.

sounds like you have a bad drive belt or maybe a Idler or Idler spring broken or has came loose.

Try this. Hope this helps. This is your chassis assembly. Look at return springs etc.

I’m happy to assist further over the phone at https://www.6ya.com/expert/layne_0fccff498c319c32

First you have to solve the "in gear" problem. No mower will crank if the drive is engaged. You have to see what is keeping it in gear and once you solve that, it will crank. I have an automatic, so I don't know how yours operates. There may be a cable or rod that moves the transmission into neutral. Look at how your clutch or brake pedal operates to determine what is not happening.
Write back.

Gary

The drive pulleys do have Shear pins where they go on the shafts. These pins do shear off once in a while. With your machine turned off try to turn pulleys by hand . If they turn easily then these could be broken. Just a thought. Try turning your drive wheels by hand with tractor in gear as the drive wheels have safety pins as well. The pins are inside the wheels or pulleys and you have to remove them to insert the pins.

Make sure the belt has not slipped off of the pulley on the engine output shaft just above the cutting blade. It is common with those type of drives for debris to make the belt hop off.