What's this pipe from the top of the rear diff supposed to go to
It is just hanging down by the props haft
I have a 2005 classic animalBild entfernt (keine Rechte)

Looks like the breather which plugs into the chassis above

Can you get another photo from above the axle, does your have a diff lock system

Yes has a diff lock but not sure if it works as light just flashes

Looks like the breather, if so it locates into the chase is above, diff lock ligh does flash when operating, it's a narrow pipe that plugs onto a metal pipe and is fed by a compressor on the inner side of the fuel tank on the chassis.

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There are two small rubber hoses, the one on top of the diff is the breather and the one that comes forward to the prop is the diff lock one.
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If you look at the chassis just above the diff you should see a round bar/cross member that should have the pump mounted on ( picture of pump: mine is a bit rusty 😄) one pipe from the diff should be on the pump and the breather mounted going into the cross member .

Thankyou all
I will try and get a better look later