Tenn. Code § 8-3704
Upon becoming a member of the retirement system to which he has transferred, such person shall thereafter be eligible for such benefits or annuities as is provided by law in such retirement system; provided, however, anything to the contrary notwithstanding, that upon service retirement his retirement allowance shall be calculated and paid by each separate retirement system of which he has been a member in the same manner as if such person were a member of such systems upon becoming eligible and making application for a retirement allowance. For the purpose of determining whether a person has been a member of a retirement system for a sufficient period of years to become eligible for any benefit or right, the aggregate number of years of service in any of the systems under § 8-3701 shall be counted.
T.C.A. § 8-3704