English to French Tech/Engineering Mechanics / Mech Engineering shifter valve

Un peu de contexte :

- The cable reel circuit includes the hydraulic tank, a pump, an oil cooler, a cable reel shifter valve and a cable reel motor/pump.
- The cable reel shifter has a high and a low relief valve (...) Oil that flows from the pump to the reel shifter valve opens a check valve which directs the oil to the cable reel hydraulic drive motor. The high pressure relief valve limits the hydraulic motor torque and diverts excess oil not required to maintain the hydraulic motor speed (to match the speed of the machine) to the exhaust port of the reel shifter valve.

Dans le mode d'emploi d'un engin de chantier. Le Grand dictionnaire me suggère 'reniflard' mais j'ai un doute... Merci beaucoup pour votre aide.