4l80e checkballs
The #8 check ball closes separator plate hole #33A and forces Third clutch feed oil from the 2-3 shift valve to pass through separator plate orifice hole #33B and on to apply the Third clutch (DIRECT) piston/ clutch pack for third gear shift.
Separator plate orifice hole #33B would be what everyone refers to as the Third feed hole in the separator plate for tuning/ drilling for shift feel.
The actual Oil flow would be:
...2-3 shift valve to the #8 check-ball and the third feed hole to a fork
...One way sends third feed oil to the third accumulator piston pushing against the accumulator oil
...The other way goes to the #11 check-ball bath-tub and closes off the reverse feed side of the circuit, then goes to the third clutch apply piston/ clutch pack.







