Is it a requirement to have back to birth records for life limited parts such as landing gears.
ANSWER: All parts that are installed on an aircraft must come from a known manufacturing source. If you can determine the origin of the parts and they have been overhauled at the prescribed intervals and the parts have not exceeded their published life, then the parts meet the regulatory requirements.
Having said that, the regulations have nothing to do with contractural obligations such as aircraft lease agreements. This is where you will normally find language such as full traceability back to birth.
Where can I find the reference?
ANSWER: The FAA, EASA, Boeing and Airbus have all issued letters or published statements pertaining to traceability back to birth.