727 issue

Good news, when a TF experiences this issue it actually doesn't affect the transmission in a destructive way. The direct clutch which is the rear clutch assembly and the rear band engage properly to move the vehicle forward, however since the torque converter is only half full, the feeling of no engagement is what it is. There is a loss of driving force until the converter fills up and fluid drive starts up. Now when GM transmissions engage, each gear adds another set of clutches so as the trans shifts higher gear more fluid level is needed to maintain pressure, filling piston chambers in each clutch pack assembly. Ford C4 and C6 among others work pretty much the same as MOPARs. It's just an annoyance.