The difference between a remanufactured and a rebuilt transmission lies in the type of work done to repair the transmission. A rebuilt transmission has its specific problem fixed and then returned to the vehicle, while a remanufactured transmission is completely disassembled and put back together in a repair shop.
Rebuilding a transmission involves removing the transmission from the vehicle, opening the case and then cleaning every component while replacing all worn out parts. Some commonly replaced parts include gaskets, bands, filters, seals and valves. The process of rebuilding a transmission is time-consuming, sometimes taking weeks, so car owners usually look for an alternative means of transport during the repair period.
A remanufactured transmission, like a rebuilt transmission, has its seals, gaskets and friction components replaced. Additionally, any component in a remanufactured transmission that doesn't fall within factory specifications is usually re-machined or replaced. However, while a remanufactured transmission costs more than a rebuilt transmission, a remanufactured transmission takes a shorter time to install. A remanufactured transmission also comes with a longer warranty period, typically over two years.
A major risk in installing a rebuilt transmission is that it may be improperly tested, so there is a possibility that it might not work any better than the previous transmission.