lawn tractor blades wont engage

I have a craftsman ys4500 lawn tractor., its 6 years old. after first post winter run the blades are not engaging correct. I just changed the belts and same issue.

So when I moved the mowing lever(to engage the blades) it used to make a thud and vibrate a touch and you knew the blades were engaged. I distinct thud and there was no question the blades were spinning it was like driving a tank with the blades spinning.

Now the blades do spin but no thud at all its whisper quiet and the blades spin up and sound like a washer machine on the spin cycle. no vibration at all I cant tell there even spinning unless I look under it. Maybe like turning on a large fan.

Its absolutely not correct but I don't see any issues anyplace under the deck

 

The blades are spinning, but they won't cut grass?

 

They spin and could probably cut grass but they sound like they might fly off the mower. Picture the sound of a CD spinning up in a drive. its nothing like it was last season.

 

They would be fixed to the drive spindle with a single center fixing bolt. Check to make sure that's tight and the blades disengage with the correct lever position. If it is and it cuts grass, I wouldn't worry about the rest.

 

You may have a bad bearing in a pulley making a lot of noise.