The transmission hydraulic control system is composed of a pump, filter, series of valves, and a control lever and linkage mechanism. The hy¬draulic control system directs oil to the clutches in the transmission.
The pump (16) delivers oil to the full flow oil filter (8). If the filter element becomes clogged, a filter by-pass valve opens and allows the oil to flow unrestricted to the priority valve (4).
The priority valve, mounted on the upper left front corner of the transmission case, functions as a restrictor valve. Spring pressure on the ball causes
a flow restriction. This restriction causes a pressure differential of 22 ± 5 PSI (1,5 ± 0,4 kg/cm2). [Later priority valves have a valve instead of the ball and the pressure differential is 25 ± 5 PSI (1,8 ± 0,4 kg/cm2 )]. The higher pressure is directed to the steering clutch controls (5) to ensure that there is sufficient pressure available to operate the steering clutches.
From the priority valve, oil is directed to the control valves in the top compartment of the transmission case. The first valve the oil contacts is the speed selector valve (6). The valve is a four position spool valve which is positioned by me-