Dual feeding increases the apply area of the 3rd gear clutches.
There are 3 methods to increase the power capacity of a clutch pack.
You increase the pressure. Typically on a 200-4R the line pressure at full TV will be 230-275 psi for a performance build. Some run it a bit higher.
You are limited, you simply cannot run 500 psi reliably, so we build a bit of additional pressure, and just as importantly, we bring it on faster.
Secondly,
you increase the friction area.
More clutches. Again, you are limited by the size of the drum and how many clutches/steels you can stack in the available space. You also trade-off steel thickness for clutch count which CAN debatebly have some negative effects.
Third,
You increase the apply area.
This is what dual feeding does. You have an apply piston that you are only using approx 1/3 of the area for 3rd, you allow it to use the full area and you more than double (approx triple) the apply area, which in theory would approx triple the power capacity of the clutch pack.
The caveat is that dual feeding requires some calibration changes to work properly on a 200-4R.
It's a proven method for TH400's TH350's, 4L80Es, and other units, and on those units it doesn't really require calibration changes.
The 200-4R needs the changes to keep the band release timing correct.
Even so,
dual feeding brings the direct clutches on firmly enough that it often causes forward drum shaft breakage on a WOT 2-3 shift.
It may be possible with a very conservative shift calibration to use the stock drum but I don't see what the advantage is, calibrate them to come on quickly and take advantage of the dual feeding.
