Differential noise / whining
 

I have a 2002 Montero XLS 4x4. The rear Diff./ carriage is making whining noise. The right rear axle has a 3/8" (10mm) gap where it looks as if the axle has pulled out of the rear diff. Is there any shear pins or snap rings ("C" clips) in the design that could be the cause of the issue? Any advice or suggestions will be helpful I'm sure. Will any rear diff. from a Montero work, or did they come with various ratios? Will a Montero Sport work? What is the range of years that will work?

Thanks in advance.