"there is a place in cal. that is afactory rebuilder"
This might even be true, but I doubt it. Terms grt thrown around and meaning sometimes get lost. "factory rebuilt" does NOT mean that it was rebuilt in "A" factory; it means it was rebuilt in "THE" factory. In the case of MB I don't know where it is.
The real difference is in implied quality. Everyone rebuilding trannies does basically the same thing. Most of the trans is reused with wear items being replaced.
Bosch Master, ASE Master, L1
33 years MB technician