Complex sentence: A minor drawback to the freewheel, particularly for drivers unfamiliar with the Saab, is that it makes engine braking unavailable except when, in later models, it could be manually engaged or disengaged by a control in the footwell.
Split into simpler sentences: A minor drawback to the freewheel, particularly for drivers unfamiliar with the Saab, is that it makes engine braking ineffective. In later models, it could be engaged or disengaged by a control in the footwell.