Cub Cadet LTX 1040 Throwing Upper Drive Belt?
 

I bought this LTX 1040 two years ago as a refurbished mower. It had been completely overhauled to factory specs, with all new parts and belts. Since then 'Ive put maybe 30 or 40 hours on it, at most. It has developed a nasty habit of throwing the upper drive belt. Not the long lower drive belt, but the smaller upper one. The belt is still in like-new condition When I say throwing, I mean it is coming completely off both the spring loaded slack adjuster pulley, and the right side (starboard) pulley. What I fail to understand is there is no way the belt can get past the guard flange on the slack adjuster pulley, and cannot get past the right pulley because the wheel well as is too close to let the belt come off. In other words, it is physically impossible for the belt to come off these pulleys, yet it DOES. Everything is in proper alignment, and there are no bad bearings or anything jamming. why is this happening? That belt can no more fit through it's guards any more than I can fit through a keyhole. So annoying. What's happening? Thank you

The idler pulley can be in need of lubrication and no longer can keep the belt taunt, then the belt gets slack and whipping around and wedges itself out like a fat mouse gets through a keyhole.
Oh.
don't fall for any "all been rebuilt" or "factory reconditioned"
its snake oil and most times they don't check the air in the tires much less put in new parts unless they are so far worn things won't function.
:bigthink:

Thank you. I know the fellow who did the overhaul. He does impeccable work But that doesn't mean the parts house didn't have the belt size called for by the mannuacturer, and he could have bought the next size one. As for the slack adjuster spring strength, I have to use a ratchet strap to pull the spring loaded slack adjuster arm enough to put the belt and pulley back on. So I doubt the spring is too old and tired Although I don't see how he belt can get past it's retainers. So, that leaves the belt being maybe an inch too big. I've done my due diligence on researching the correct factory-prescribed belt sizes, and that information is not to be found anywhere. I wonder if anybody here knows the correct upper and lower drive belt sizes, as factory-recommended.

Sold at Lowes....
Are you sure the belt you are using is 5/8" wide??

https://www.lowes.com/pd/Sunbelt-42-...ors/1001829572

Thank you for these answers. I got the upper drive belt back on and got the rest of the yard finished up with no problems. but now after 2 of these mishaps, I can never trust it again. That belt can come off any time again for no reason. And it's one big PITA to re-install it. But I have a last question. No matter how gently and smoothly I push the engage pedal, it often will "snatch" into moving the tractor, casing me to be lurched in the seat. What might be the cause of that? Thank you