Griner transbrake is a fluid release design. Pressure acts on a differential area on the transbrake valve and closes off(pushes out the valve) the pressure from the transbrake hydraulic circuit when the button is not depressed. When the button is depressed, the solenoid pulls in and allows oil pressure to flow to the front clutch and low/rev band. When the button is released, solenoid pull force is absent, and the fluid pressure acting on the differential area forces the transbrake valve out, exhausting pressure from the direct clutches >>>> LAUNCH. The early solenoids do not have internal springs in them. The later ones do, but the spring is not necessary. Fluid release thru the differential area valve is what makes it function. Solenoid winding resistance should be about 1.5 ohms.

John