I need to know the route of the drive belt around the pulley syst

Sounds like the belt might be smaller/shorter than the required belt, not providing enough clearance to the spindle pulley(s) when tension is release. Might verify correct routing of the belt as well.

it could be but if it kept going with the clutch in i would guess the belt is the wrong one or it was put on incorrectly. not saying you don't know what you are doing but it happens a lot where the belt was routed wrong and did the same thing you are saying. be sure it is routed correctly.

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.

I'm not sure what you're asking for exactly, but you can find a diagram of the Craftsman LT2000 here:

https://mowerslab.com/craftsman-lt2000-drive-belt-diagram/

Route the deck drive belt between the two inner, forward pulleys and then out and around the outer blade pulleys.

With the model number you have you can search for craftsman parts and go to sears and enter the model number and select the deck and find the replacement belt routing sticker for your deck. It goes on the top, left, front.

The belt comes from the motor pulley in between the pulleys in the middle and around the back of them, then out to the front side of blade pulleys, around the outside and straight across the back from blade pulley to blade pulley. Not a hard routing. If looking down on the deck from the seat it will look like an inverted T. Watch out for the belt keepers that help keep the belt aligned in the pulleys, may need to gently retract them to get belt in the pulley.

Hopefully this will help

This belt is easist to install with the deck all the way down. Make sure there are no burrs on any of the pulleys, (will eat up your new belt in short order), also make sure that the 2 drive pulleys for the blades turn freely, (may have grass impacted around them, you may need to remove the 2 guards on top of the deck to clean, (if they do not spin eaisly). Triple check to make sure the belt is properly routed, one mistake and your belt is broken as soon as you engage. With the engine OFF, engage blades to check tension. If the belt is still loose, you likely have it routed incorrectly.

Are you saying the blades start turning when you crank your mower? If so, you either have the wrong belt (should be # 144959) or have it routed incorrectly. Belt should go straight across the back between the spindle (blade) pulleys, then, in front of those, to the inside of both smaller, idler pulleys and then to the engine. Be sure to work the belt down between the pulleys and the flat, metal belt keepers on each idler pulley.