[Engine_Tech]

I agree...I've never heard of this.

-did you buy it new?
-did this problem start suddenly? How long did the original last?
-got some photos of the belt routing?

 

[Engine_Tech]

That is extremely odd. That ribbed belt is also very, very strong (developed for the uber powerful 355D) so it should have no problem on your 345. That's the "old 54" deck too, which never had any belt issues (neither did the later 54C, but regardless...).

A primary deck belt should last hundreds of hours no problem, regardless of the cut height. It's not going to run perfectly horizontal, and that's OK. Something is really, really odd about your tractor + deck.

Get us as many photos as you can of the belt on the tractor, and them maybe of the deck removed. Photos from the top so we can see all the components. Many of us have 54" decks and 345's, we'll get it worked out.

 

[Engine_Tech]

I've attached some photos of a 54" of roughly the same vintage. My neighbor isn't using it right now, so it's in storage in his barn. As you can tell, the pulley isn't actually straight if you look at it from the front. By straight I mean in the same plane as the secondary belt. It actually tilts down a little on the right (from the seat). From from the side, it appears to tilt rearward a tiny bit (toward the back of the tractor). So the front is actually tilted upward, which would help with the belt angle. Neither tilt is extreme, so I'm not really sure it would help your problem. But here you go.

And I hate to say it, but why did you wait so long to try and get this resolved? John Deere is by far the best company I've ever seen in trying to make things right and keeping customers happy. I've seen them bend over backwards for folks - inside and *reasonably* outside of warranty. It's been long now though...

And why a new PTO clutch and all the other parts? I've got a bad feeling that throwing parts at it won't help. Those arms are powdered metal, so they don't bend or get out of whack. They just break.

I wonder if the mounting plate welded to the rear of the deck is tweaked or welded wrong? That is honestly about the only thing that could throw off that double pulley angle. A long pry bar and a hammer can probably correct that.

Hopefully some others can take pictures of the belt and pulley angle on their 345 w/ the old 54 deck. Let's not go totally by this one.

FYI, this guy has run this deck probably 300 hours over 10 years and it's still on the original primary and secondary belts.

 

[Engine_Tech]

If it's a '99 model, it's a straight 345 w/ 54" "Mulcher Compatible" deck...i.e. "the old 54". It's not the later 54C Convertible deck.