I just relaced the same belt on the same model number tractor yesterday and it was an 88"x1/2".
The drive belt is a Craftsman #140294 The deck belts are Craftman #'s 180808 & 174368
you probably have a bad bearing
Gates
i changed the belt on my 42' craftsman riding mower, belt route is right but may belt is burning up. I don't know if my levers are connected right.
maybe your deck is too low
It might be the bearings are shot in your jack shaft.
You have probably broken the drive belt. With the mower turned off, lie on the ground and look underneath the mower. There is a deck belt and a drive belt. The drive belt is the upper belt. Grab the upper belt and see if it is broken.
You may have installed the wrong size belt? One of your spindles may be bent. Double check to see that your spindles are not bent and that you have purchased the correct belt for your mower.
Usually there is a problem with the belts that drive the blades, after you stop the mower. Take a close look at the belts and assure that the belt is tracking and the pulleys are aligned. If you are unsure of the belt routing recheck the manual.
There should be a belt diagram on the underside of the left foot rest.
The belt length for a Craftsman tractor LT 4000 42 is 96 inches by three-quarter inch. This is assuming the same 42 inch mower deck is still in use.
You probably blew a belt.