Device for adjusting a relative rotational position of a gearwheel and a ring gear which are coaxially mounted

Device for releasably setting a relative rotational position of a gearwheel and a ring gear which are coaxially mounted, comprising means for applying a spring force to at least one of the gear wheel and the ring gear so as to form a positive connection between the gear wheel and ring gear, and decoupling means for counteracting said spring force-applying means so as to reduce the spring force applied thereby, said decoupling means including a pressurized hydraulic fluid, a fully sealed pressure chamber wherein said hydraulic fluid is received, said pressure chamber being defined by the gearwheel and a clamping disc which presses the ring gear under the action of said spring force against the gearwheel, and adjusting means disposed in said clamping disc for adjusting the pressure of said hydraulic fluid received in said pressure chamber.