A surgical instrument having a transmission assembly, a transducer, and ahandle assembly isconfigured for coupling the transmission assembly to the handle assembly usinga lockingmechanism. The locking mechanism is operable to restrict the rotationalmovement of anactuator coupling member and the transducer relative to the handle assembly.The lockingmechanism may also be operable to lock a trigger of the handle assembly in afirst position. Aninner tubular actuating member of the transmission assembly may be threadablyattachable to theactuator coupling member or the actuator coupling member may include alatching mechanism tocouple to a flared portion of the inner tubular actuating member. A waveguideof thetransmission assembly may also be threadably attachable to the transducer. Inone alternative,the trigger may be configured to operate the locking mechanism, either in thefirst position orwhen pivoted distally to a third position.
