Can I send my Xbox 360 to microsoft without Guarantee?

you can, but you will have to pay for delivery / pickup and repairs that may occur etc

Do you mean without warentee? Check online at xbox website and register your consol, depedning on the issue it's having it may still be under warentee. It will tell you.

You have to register it anways in order to have Microsoft repaire it, otherwise you may not get it back.

Go here to register your consol:

http://support.xbox.com/support

Im pretty sure you can, you just have to have proof of the Warranty i think, i never had it done, but i think you can without a guarantee.