If you can see the output shaft splines, the flange has come off. You may be able to reinsert it. I would be very carefull with your examination of the output flange. It isn't that expensive and is easy to replace the shaft isn't. Be sure to replace the nut.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician