In power-split transmission systems developed by Dana-Rexroth Transmission Systems, a crucial role is played by the adjustable mechanical couplings performed by clutches operated by means of suitable electrovalves. We propose here a reset control scheme with adaptive feedforward action to perfectly track a known smooth reference for the current flowing in the valves. Formal properties of the scheme are first established and then a simplified approximated version is proposed for a simple implementation on the real-time control system. We report on simulation and experimental results both illustrating illustrate desirable responses. Simulations also confirm the theoretical results about asymptotic convergence of the estimates to the values of the unknown valve parameters.