A different approach is to make use of a variable displacement pump.  Once the pump is configured for very low displacement, it produces a lower volume of oil flow, producing the hydraulic motor(s) to turn far more gradually. Like most automotive know-how, you will find benefits and drawbacks to CVT gearboxes https://andresegeaw.bloggazzo.com/33238156/new-step-by-step-map-for-gearbox-cvt