How long after retirement do you have to submit a disability claim? What is a good organization to assist with this?

1SG, I don't know the time window on filing for a claim, but many of the Service organizations like VFW, American Legion, Disabled American Veterans (DAV), Vietnam Veterans, etc. can help you with that information.  Many of these organizations have offices INSIDE  VA hospitals to help you.  Typically you bring your documentation, DD 214, medical records, etc, and they can enter your information onto the forms via computer and deliver the claim directly to the proper person.  I used the VFW representative, but any of the organizations will be helpful.

One more thing, regarding documentation, it is often overlooked to have statements from a spouse, or a family member describing how your disability has an effect on your life, or your relationships.  Even disabilities such as tinnitus or hearing loss takes a toll on family members with one's inability to hear some sounds, or with the inability to get to sleep with that incessant ringing in one's ears.  These can be valuable insights to those evaluating your claim.