If this is a RWD Ford unit, then it is important to pull down the pan and filter, and then re-torque all the valve body bolts evenly to 110 inch lbs. These small diameter bolts have 8 and 10mm bolt heads. The thin gasket between the valve body and the case compresses over time and these bolts loosen significantly and allow cross-leaks, allowing shudder due to partial engagements. Do not use DexIII/Merc unless for an extremely short flush/run, say for less than 1000 miles. You can get good-but-cheap SuperTech MerconV for $3-3.24/qt. The Valvoline MercV fluid is "full synthetic", but probably GrIII from looking at the price. A true upgrade fluid IMO would be M1 MerconV or Amsoil ATF. Lubegard Red does not help with shudder much in my experience, but the tube of ShudderFix does work, or a half bottle or so of Lubegard black. Too much friction modifier could cause clutches/bands to slip too long before locking up during each shift. You want just enough of the anti-shudder additive to get rid of your shudder, then add no more! Don't put in any anti-shudder additive if the shudder stops with the new fluid and valve body re-torque alone.