ORIGINAL: gerwen
Is the xxx-nt diff held together with a nylon nut? It sounds like it is worn out. Replace it. Maybe use some loctite in there (sparingly) to hold it better.
...checking further back in the directions...

yes there is a nylock nut that needs some massaging[:-]
thanx gerwen...just need to flip back more pages of the manual...time to rip apart[:'(]