Fluid Pressure Directed in Preparation for a Shift to Fourth Gear

2345 fluid is routed through the 2-3 shift valve (371) into the 345 fluid circuit.

345 fluid is routed through the X-4 ball check valve pocket. In some transmission models there is a ball check valve present which would force 345 fluid through orifice #25.

345 fluid is routed to the 3-4 shift valve (345) where it is blocked by the valve in preparation for an upshift to fourth gear.