An improved braking mechanism (100) is provided for use in conjunction with a change gear transmission (50) that is selectively engagable with a vehicle engine (4) by a clutch (3). Mechanism (100) has a piston (22) slidably received in a primary fluid chamber (34) that is operative to cause mechanism (100) to act as an inertia brake upon establishment of a first set of predetermined operating conditions. Piston (22) is also slidably received in a secondary fluid chamber (36) that is operative to cause mechanism (100) to act as a hill holding brake upon establishment of a second predetermined set of operating conditions.