holley 4010 kickdown?

I gotta say that it's odd that shifting manually makes any difference in the shift quality on the 2-3 shift because no matter how it shifts (manually or automatically) the throttle pressure is regulated the same whether it's in drive or you manually shift it. But as Rob said you really need to get it fixed or your taking a huge chance of destroying the trans. The "kickdown" as alot of people call it isn't really specifically for kickdown although it functions as such. It is a throttle pressure regulator for the trans. If it's not hooked up or working correctly the hydraulic pressure on the clutch plates and band servo's will be low and let them slip as you've seen by it slipping in drive. It doesn't take much slippage of the clutch plates and/or bands to trash the trans.