I had the deck rebuilt at the end of last year and also replaced the belt. This year the tension on the belt lessens as I lower the deck. In other words, when the deck is at the highest setting (4) there is tension. As I lower it, the tension lessons and on #2 setting, there is no tension at all. I work on the tractor all the time and am perplexed at this. Also, the adjustment on the deck is all the way. Its probably something stupid that I'm overlooking. Any help would be appreciated. It's a john deere L100

Hi,
There are in fack six different height slots I believe. If you use the OEM belt and everything is set, the only thing that comes to mind is that the front hanger mount(the one the zig-zig rod and half sphere hook onto) is replaceable and held in place by two bolts. Striking some object with the front of the deck can bend it rearward which affects the decks position.
See link below.
Peace,
Clarke