Deck is loud and shakes some.

[Allergic2Grass]

Not sure what step I missed or it's just worn part?

Craftsman 917.256611

Took the deck apart in winter and worked on it when. Replaced mandrels and blades and kept old pulleys.

Now the deck shakes and it's loud unlike before. Not sure what's wrong. But my belt looks loose?

 

[Rivets]

If it came into the shop like that the first thing I would be checking and probably replacing are the spindle bearings.

 

[bertsmobile1]

By mandrels I am assuming you replaced the entire unit and just reused the old pulleys .
If so start with double checking that the blades are on properly.
Very common for the blade to slip off the star so when done up tight with a rattle gun, the blade is out of balance.
After that look at the belt for a split or gap
Check that th e pulleys are sitting square on the end of the shafts & not wabbeling
Finally check all of the idler pulleys , they must spin smooth& silent or the bearings are gone.
If the deck has pulley brakes ensure that the brakes fully disssengage from the pulleys

 

[Allergic2Grass]

By mandrels I am assuming you replaced the entire unit and just reused the old pulleys .
If so start with double checking that the blades are on properly.
Very common for the blade to slip off the star so when done up tight with a rattle gun, the blade is out of balance.
After that look at the belt for a split or gap
Check that th e pulleys are sitting square on the end of the shafts & not wabbeling
Finally check all of the idler pulleys , they must spin smooth& silent or the bearings are gone.
If the deck has pulley brakes ensure that the brakes fully disssengage from the pulleys

Yes sorry replaced the entire thing with new blades. Only the pulleys ,belts and tension spring were reused

 

[keakar]

Not sure what step I missed or it's just worn part?

Craftsman 917.256611

Took the deck apart in winter and worked on it when. Replaced mandrels and blades and kept old pulleys.

Now the deck shakes and it's loud unlike before. Not sure what's wrong. But my belt looks loose?

its easy to see in the video, the rear idler pulley has come loose and/or the bearings in it have fallen out. its about ready to sling the belt off and fly completely off the deck

replace both of the idler pulleys, they run like $15 each on ebay, and it will be fine again but after removing the belt you need to double check the spoindle bears dont have play in them or if they grumble when spinning, if they are replace them as well