I think you're misunderstanding my terminology. The carrier bearings (plural) are the ones inside the housing, on each side of the ring gear. They support the differential assembly. That Grumman van will probably have the same Eaton rear end as the 3/4 ton and 1-ton trucks. If it's one of the bigger van bodies, it might step up to the 1 1/2 ton chassis with an upsized version of the same type of rear axle. Either way, it's time to pull the axle shafts, drop the center section out, and start looking for trashed bearings. You might be able to get an idea of what's going on by draining some of the grease out of the rear end, and check for a metallic shine, or even chunks of metal.
Jerry

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