extremely soft 2nd to 3rd shift

since the rear clutch is already engaged while in second gear we can eliminate that. so that leaves the kickdown band..(releasing to slowly) or the front clutch...(engaging to slowly) with that said the kickdown band is applied by the kickdown servo. The piston is applied by line pressure...release is achieved by line pressure and return spring force combined. check the servo spring...if that is ok check the little orifice in the large piston...if that is plugged at all the release will be slow. The front clutch could have a piston seal that is leaking but not as likely because you aren't slipping. That line pressure adjustment may be a problem too...