New mower blade Installation

[warksfarmer]

Ok what am I doing wrong.
New gearbox put onto a JD F1145 mowing deck. New pto shaft as well.
When we start it up it unwinds the the cutting blades of which there’s 3 of them. It’s not the same one all the time and seems to do it when we are powering it down rather than at start up. There’s also a vibration as it powers down.
The blades are attached with an air ratchet so as tight as we can get them. The blades are not hitting each other under the hood and the belt is on correctly.
The only thing we can think of is that the new gearbox is turning in the opposite direction to the old one it’s replaced? The pto drive out of the mower itself has not been touched and turns freely etc.
It’s got to be something stupid but now having spent far to much time on it I can’t see the wood for the trees I don’t think.

 

[bobk]

The outside disc always turns in to the mower . suspect you've got the geometry wrong

 

[Dave W]

John Deere decks turn the opposite way to Kubota decks etc. So it's entirely possible the blades are spinning backwards.
have you actually tested to see which way they spin?

 

[milkloss]

Not sure an air ratchet is that reliable for getting things tight..... I don't expect it's the problem but I'd like a proper hand tool on it to check.

 

[Dave W]

Not sure an air ratchet is that reliable for getting things tight..... I don't expect it's the problem but I'd like a proper hand tool on it to check.

The blades are designed like an angle grinder nut. If they slip they tighten up. But if the wrong gearbox has been fitted and the blades are spinning backwards then they will undo if they slip.

 

[warksfarmer]

The outside disc always turns in to the mower . suspect you've got the geometry wrong

It’s 3 blades and it’s side discharge so they all need to turn the same way?

 

[bobk]

It’s 3 blades and it’s side discharge so they all need to turn the same way?

I'm not conversant with this mower , @Dave W is .

 

[warksfarmer]

John Deere decks turn the opposite way to Kubota decks etc. So it's entirely possible the blades are spinning backwards.
have you actually tested to see which way they spin?

Yes it looks ok as it’ll start to throw grass out the side discharge and when we lift up you can see the grass has been cut towards the side discharge.
The gearbox is a proper JD part supplied by JD so if they make a left and a right then it could be what you suggest but there’s only one way to fit it due to the pto drive from the tractor unit.

 

[Dave W]

Yes it looks ok as it’ll start to throw grass out the side discharge and when we lift up you can see the grass has been cut towards the side discharge.
The gearbox is a proper JD part supplied by JD so if they make a left and a right then it could be what you suggest but there’s only one way to fit it due to the pto drive from the tractor unit.

New blades?

 

[warksfarmer]

New blades?

No the old ones as they were new in the spring. If I sent you some pictures tomorrow would you know if something looked wrong?

 

[Dave W]

No the old ones as they were new in the spring. If I sent you some pictures tomorrow would you know if something looked wrong?

Maybe. Did you have the blades off to fit gearbox?

 

[warksfarmer]

Maybe. Did you have the blades off to fit gearbox?

Just the centre blade as you can’t change the gearbox without taking it off.