Two new fuel-efficient transmissions for light-duty trucks are being developed by Chrysler Corp., and that should soon translate into some big orders for high-volume production equipment, company sources say. Known as the 45/55 RFE and the 46/47 REE, the two new automatic transmission families could be out as early as 1998 if the simultaneous engineering work involving machine tool suppliers begins soon. Chrysler sources say the new transmissions will need a substantial number of new large die-casting and transfer-type milling, boring and drilling machines for aluminum cases.